Affectionate touch of relatives:
A. Hugging and kissing relatives:
It is forbidden to hug or kiss any of one’s relatives, including one’s adult sister or aunt [and uncle, niece, nephew, cousins] and the like, with exception to a father/mother and daughter/son, as will be explained. This prohibition applies even though there is naturally no physical attraction towards the relative, and one receives absolutely no pleasure at all from the act of hugging or kissing them. Hugging or kissing such relatives is a most deplorable act, and is a forbidden act, and is the doings of a foolish person, as one is not to bring himself in physical closeness with any relative of the opposite gender, whether she is an adult or a child. [Relatives are not to hug or kiss children of the opposite gender beginning from nine years for a boy and three years for a girl, with exception to one’s children, grandchildren, and siblings, as will be explained. An uncle is thus not to hug or kiss his niece once she reaches three years of age and an aunt is not to hug or kiss her nephew once he reaches nine years of age. It is forbidden for a cousin to hug or kiss his cousin of the opposite gender, once he/she reaches the above age.]
Parents, Grandparents, children and grandchildren: Kissing and hugging is permitted between parents and their children, even if they are of the opposite gender [and even if the children are now adults]. Thus, a mother may hug and kiss her son [of any age] and a father may hug and kiss his daughter [of any age]. [See Q&A regarding if she is married!] Kissing and hugging is likewise permitted between grandparents and their grandchildren of the opposite gender.
Brother/sister who are still children: It is permitted for one to hug or kiss his sibling of the opposite gender even if they have reached the age of nine years for a boy and three years for a girl. It is thus permitted for a brother to hug and kiss his three-year-old sister. [It is likewise permitted for a sister to hug and kiss her nine-year-old brother.] This allowance applies until the child begins to become physically developed which is approximately 11 years old for a girl and 12 years old for a boy. [However, some write that one is to be careful in this matter from age six.]
May a parent/grandparent hug a married daughter/granddaughter?
Some Poskim rule it is permitted for a father or grandfather to hug and kiss his daughter/granddaughter even if she is married. Other Poskim, however, rule it is forbidden for them to kiss or hug a married daughter/granddaughter. Practically, it is permitted to do so, although one who desires to be stringent upon himself is blessed.
Relatives showing affection in public:
It is permitted for a father/mother/grandfather/grandmother to engage in non-affectionate touch with their daughter/son/granddaughter/grandson even in public. [It is possible to learn in the Poskim that it is however forbidden for them to engage in affectionate touch in public, such as hugging and kissing. On the other hand, one can argue that affectionate touch between such close relatives does not lead others to any immoral thoughts. Practically, since in most situations it is not obvious to others that the two are father/daughter etc one is to be stringent, and so rule some Rabbanim of today. However for a parent/grandparent to hug their young child in public is certainly permitted.]
May one shake hands with his/her sister/brother?
If a parent sees a male relative hugging or kissing their daughter who is above age three, is he obligated to stop them from doing so?
One is not required to protest the relative, especially in a case that the relative may take this personally. However, one should explain to the relative and daughter the Halachas of touch, at an appropriate occasion.
The eradication of the Yetzer Hara of attraction for relatives:
The Talmud states that in the times of Nechemia, after the destruction of the first Temple, the Sages prayed to G-d for the spiritual power in charge of the Yetzer Hara of idolatry to be given to them, so they can destroy it. After they were successful in suppressing it, seeing that it was an auspicious time, they prayed to also be given the inclination for sexual relations. This request too was granted, and they captured the spiritual force in charge of sexual lust. However, destroying this inclination would cause children to no longer be born. They kept it in captivity for three days and saw that in that three-day period, no eggs were layed. Instead then of destroying the spiritual force in charge of the inclination, they blinded it, and this diminished the lust and attraction that one has towards relatives.
B. Placing head of relative in one’s arms:
It is forbidden for even close relatives, such as a father, grandfather and brother, to place their heads on the laps or on the chest of their daughter, granddaughter or sister. [The same applies vice versa.] Thus, if the above relatives need to check each other’s hair for lice, they may only do so without having the head of the relative rest on their body.
C. Checking a relative’s head for lice:
It is permitted for close relatives, such as a father, grandfather and brother, to have their heads checked for lice by their daughter, granddaughter or sister. [The same applies vice versa.] This may be done even in public, in the face of others. However, it is forbidden to place their heads on one’s lap or chest while the hair is being checked, even in private. [It is forbidden for a daughter in-law to check her father-in-law’s head for lice.]
D. Washing a relative’s head:
It is permitted for a daughter or daughter-in-law to wash her father’s, or father in-law’s head [i.e. Chafifa]. [However, it is best for a daughter in-law to be stringent not to do so.]
 Michaber Even Haezer 21:7; Rambam Issureiy Biyah 21:6; Shabbos 13a “Ula stated that any closeness is forbidden as we say to the Nazir Sechor Sechor…”; Avoda Zara 17a; Bach in Kuntrus Achron 21; Chochmas Adam 125:1; Igros Moshe Y.D. 2:137; Nitei Gavriel Yichud 53:1; See Meil Tzedaka 19; Od Yosef Chaiy Parshas Shoftim p. 151
A Tzaddik: Although Ula himself made the above statement prohibiting any physical engagement between relatives, Ula himself would kiss his sisters by the hand or by the chest [Bei Chadaihu]. [Shabbos ibid] This is because Ula was a complete Tzaddik, and he knew that he would not be led to any immoral thoughts, as it was like kissing a wooden board. [Chelkas Mechokek 21:8; Beis Shmuel 21:14; Tosafos Shabbos 13a; Likkutei Sichos 6:415] Likewise, Ula would not come to do so with any other women, as he was a complete Tzaddik, and hence there is no reason to decree against him kissing his sister. Other people however may learn to hug other women if this were to be allowed. [Igros Moshe ibid] However, some explain that it is permitted to hug a relative if one has no affection, and the intent of Ula to prohibit hugging relative, is only if one has sexual pleasure from doing so. [Meil Tzedakah 19; Vetzaruch Iyun, as this contradicts the entire ruling of Michaber/Rambam ibid] Another example of the above allowance for Tzadikim can be found in scripture where Yaakov kissed Rachel. [See Meil Tzedaka 19; Od Yosef Chaiy Parshas Shoftim p. 151]
Yaakov kissing Rachel: The Torah [Bereishis 29:11] relates that Yaakov Avinu hugged and kissed Rachel, his first cousin, when he first met her. The Mefarshim and Poskim deal with why he did so, and how this does not contradict the above ruling. Some say that this was the accepted form of greeting in those times, and since they were cousins it would not be viewed by anyone as an erotic act. This is similar to a doctor touching a woman for medical reasons. [Midrash Raba Vayeitzei that it was a kiss of “Kirva”; Meil Tzedaka 19; Od Yosef Chaiy Shoftim p. 151] Others say that he kissed her on her forehead, or shoulder, and not on her lips. [Rabbeinu Bechayeh ibid] Alternatively, she was a small girl [and not an adult]. [Rabbeinu Bechayeh ibid] Others say that his was a mistake [See 2nd Pirush in Midrash Raba ibid] and Yaakov was in truth punished for doing so. See Tanya chapter 47; Torah Or Vayeitzei and other Chassidishe Sefarim where this matter is explained according to Penimiyus Hainyanim.
 The Michaber ibid states one’s father’s sister, although obviously the same would apply to one’s mother’s sister.
 See Chochmas Adam ibid for a list of all the Arayos
 Michaber ibid; Rambam ibid; Bach in Kuntrus Achron 21
Other opinions: Some Poskim imply that there is never a prohibition to hug and kiss a relative [even of permissible marriage] if one is doing so without any sexual intent or pleasure, and is merely done out of Derech Eretz and the way of the world. [Implication of Meil Tzedaka 19 in his answer of Ula; Od Yosef Chaiy Parshas Shoftim p. 151 based on Midrash Raba Vayeitzei regarding Yaakov and Rachel and on Heter for a male doctor to have a female patient; Vetzaruch Iyun, as this contradicts the entire ruling of Michaber/Rambam ibid]
 Michaber ibid; See Beis Shmuel 21:14 who uses the term “forbidden” and not just a Davar Issur as writes Michaber; See Bach in Kuntrus Achron 21; Otzer Haposkim 21:51 in name of Batei Kehuna; See next footnote
 Michaber ibid; Rambam ibid; See Bach in Kuntrus Achron 21
Is this a Biblical or Rabbinical prohibition? Hugging, kissing, and other touch of relatives which is done for the sake of sexual pleasure, or from which one receives sexual pleasure, is a complete Biblical prohibition which is liable for lashes and is to be protested against. [Bach in Kuntrus Achron 21] Thus, hugging and kissing relatives who one can marry, such as a niece, or cousin, is a complete Biblical prohibition which is liable for lashes and is to be protested against. The reason for this is because one has benefit and pleasure from such contact, and is therefore include in the Biblical prohibition of touching an Erva in a form of Chiba [affection]. It is therefore Rabbinically forbidden even for a Tzaddik to hug and kiss such relatives, even though he has absolutely no erotic thoughts, as this appears as a forbidden act of affection. However, hugging and kissing other relatives with whom marriage is forbidden, and there is no natural attraction to them, such as a sister and aunt, is only a Rabbinical prohibition due to a decree that one may come to do so with other relatives. However, there is no Biblical prohibition involved, being that the Biblical prohibition only applies if one does so “Derech Chiba” in a way of pleasure. One is therefore not required to protest against one who does so, if one assumes that they will not listen. [Igros Moshe ibid; see Bach in Kuntrus Achron 21 that whenever one has a lust and pleasure for the touch of the relative, it is Biblically forbidden, even if one cannot marry them, and it is only when one has no feelings of lust and pleasure, which is usually the case, that this prohibition does not apply.]
 It does not state explicitly in Poskim the age from when hugging and kissing is forbidden. However, seemingly it would only apply by a child who has reached the age of Biyah, which is three years for a girl and nine years for a boy. [Implication of Beis Shmuel 21:9; Michaber 22:11 and Beis Shmuel 22:15 state regarding the start of the prohibition of Yichud that it begins from age nine for a boy and three for a girl and the same would seemingly [and certainly] apply towards affectionate touch; Beir Moshe 4:145; Nitei Gavriel 53:1]
 Rav SZ”A in Avnei Yashpei p. 189
Other opinions: Some Poskim rule an uncle may hug and kiss his niece until she becomes physically developed, which is usually not before age 11. [Beir Moshe ibid] The reason for this is because a niece which has not yet reached age of maturity is not an Ervah at all. Vetzaruch Iyun as the Sages prohibited Yichud with her from age three.
 Michaber ibid; Kiddushin 80b; Kitzur SHU”A 159:10
 Perisha 21:7; Beis Shmuel 21:15; Beir Heiytiv 21:15; Taharas Yisrael 21:17; Chochmas Adam 125:6
If the daughter/granddaughter/mother/grandmother is a Niddah: The above allowance applies even if the relation is a Niddah. [Betzeil Hachochmah 3:12]
 Chelkas Mechokek 21:10 based on Kiddushin 81b; Beis Shmuel 21:14 [see there for a long discussion on this topic]; Pischeiy Teshuvah 21:5; Igros Moshe ibid
 Implication of Michaber 21:7 “older sister”; Chelkas Mechokek 21:9-11; Beis Shmuel 21:14; Chochmas Adam 124:6
The reason: As this is done simply Lesheim Shamayim for the sake of showing closeness to one’s relative, and not for the sake of showing closeness of a marriage nature. [Chelkas Mechokek ibid]
 Based on Michaber 21:7 and Admur 73:3 who gives this age for parents with children in terms of sleeping together, and the Chelkas Mechokek 21:11 and Beis Shmuel 21:14 applies the same law to a younger sister, and certainly the same would apply to hugging and kissing [which is less severe than sleeping with each other unclothed, as brought in Beis Shmuel 21:15]
 Admur ibid; Chelkas Mechokek 21:12; Chochmas Adam ibid; Igros Moshe 2:144; Nitei Gavriel 53 footnote 10
 Nitei Gavriel 53 footnote 10
 Beis Shmuel 21:14 that when both are clothed there is no prohibition to sleep together even if she is an adult and is married; Pnei Moshe 21:5; Beir Heiytiv 21:14; Aruch Hashulchan 21:10; Taharas Yisrael 21:17; Nidchei Yisrael 24; Divrei Yatziv Even Haezer 36; Chochmas Adam 125:6 concludes with a Tzaruch Iyun; Betzeil Hachochmah 3:12
 Mishneh Lamelech on Rambam 21:6-7; Nesivos Shabbos 13a; Meiri Kiddushin 81b; See Betzeil Hachochmah ibid
 Betzeil Hachochmah 3:12 as rule majority of Poskim ibid
 Betzeil Hachochmah ibid; Beir Moshe 4:145; Igros Moshe Even Haezer 1:60 and 4:63; See also Od Yosef Chaiy Shoftim 21 that a Baal Nefesh is to be stringent to himself. [does not specifically stipulate regarding daughter who is married].
 See Beis Shmuel 21:12; Taz 21:1 that by the above relatives doing acts of non-affection acts in public [such as checking each other’s hair] does not arouse immoral thoughts being that everyone understands that they do not share an incestuous relationship.
 As the above Poskim only permitted these relatives to check lice in public, which is not an affectionate touch, while by an affectionate touch, such as hugging and kissing, certainly it can arouse immoral thoughts in the onlooker.
 So is implied from the ruling of the Taz and Beis Shmuel ibid that there is no Zichron Tashmish by such relatives
 So rules Hagaon HaRav Yaakov Yosef Zal, stating that those fathers who hug their older daughters in public are Amei Haretz and are causing others to stumble.
 Pashut, as people do not view this erotically.
 Rav Elyashiv in Koveitz Teshuvos 2:20; Mishneh Halachos 4:186
 The reason: As the Sages only forbade clear acts of affection, such as hugging and kissing, and not acts of respect such as shaking hands.
 See Igros Moshe Y.D. 2:137
 Yuma 69b
 The Talmudic statement is expounding the verse in Nechemia 9:4 which states “Vayitzaku El Hashem Bekol Gadol”
 Taz 21:10; Beis Shmuel 21:12
 The reason: As doing so involves too much affection. [ibid]
 Taz 21:10; Beis Shmuel 21:12
 The reason: As this is not an act of affection and will not cause others to have erotic thoughts of them. [ibid]
 Rav Akiva Eiger Y.D. 392 in name of Beis Yosef 135
 Michaber Y.D. 392:2
 Rav Akiva Eiger Y.D. 392 in name of Beis Yosef 135