Co-sleeping-May boys/men sleep together on the same bed?
It is forbidden for two men/boys to sleep together in the same bed. This applies even if the men are married, and certainly if they are both single. This applies even if they are brothers. One is to protest against one who does so. This certainly applies in this generation. [Thus, in Yeshiva, Bochurim are never to sleep together on the same bed. The same applies in hotel rooms that there should only be one man/boy on a bed. Hence, when making reservations, it is the responsibility of the Yeshiva/camp to make sure that everyone will have a place to sleep without needing to double up on the same bed. The same applies when friends order a hotel room, that only one person should sleep on each bed. The same applies during camping trips that when sleeping in a tent, they may not sleep under the same blanket or sleeping bag, and are each to have their own corner in the tent. Likewise, during sleepover parties, boys may not sleep on the same bed, whether they are friends, relatives, or brothers. Even more so, one may not sleep on the same bed as a sibling of the opposite gender. It is the job of the parent to ensure this and prevent their children from innocently stumbling on a matter of severe prohibition.]
From what age does the above restriction begin from?
The above restriction begins once one of the boys reach the age of adulthood [i.e. puberty, or 12 years for a boy, or embarrassment to be seen naked]. Nonetheless, it is proper to be careful in this once one of the boys has reached age 6, and at the very least from age 9.
May three or more boys/men sleep together on the same bed?
From the letter of the law, this is permitted to be done, although due to it possibly arousing forbidden thoughts, it should not be done.
Does the above prohibition apply also to girls/woman co-sleeping on the same bed?
A letter of the Rebbe Rayatz on the subject:
In answer to the letter….The supervision over the dormitories [in Yeshiva’s] is very much necessary. It is a great responsibility given over to the heart…..as aside for the basic supervision over the boys that they read Kerias Shema Sheal Hamita, and cover their heads when they sleep, and wash hands and say Brachos in the morning, aside for all this, and mainly, periodically [the dorm councilors] need to visit the dormitory when the boys are sleeping to make sure that two boys do not sleep on the same bed etc etc, as regarding this the children and adolescents transgress as they are not informed of the great sin that they are doing to their souls, and body r”l, and they must be guarded very well.
 Implication of Michaber E.H. 24:1 who concludes today to distance even Yichud of two men, and certainly sleeping in the same bed would be forbidden; Rebbe Yehuda in Mishneh Kiddushin 82a “Two single men are not to sleep with the same sheet”; Tana Dvei Eilyahu Ish Shalom Drasha 18; Beis Shmuel 24:1 “One is required to distance from it” [and that this applies even according to the Bach 24 who argues on Michaber ibid and permits Yichud amongst males]; Chelkas Mechokeik 24:1 “Certainly two single men are prohibited to lie together” [and that this applies even according to the Bach 24 who argues on Michaber ibid and permits Yichud amongst males]; Beir Heiytiv 24:1; Shelah p. 99; Tochachas Chaim [Falagi] Bereishis Parshas Vayeitzei p. 125; Kitzur SHU”A 151:2; Kaf Hachaim 240:25; Nidchei Yisrael 24 [of Chofetz Chaim]; Chemdas Shlomo 204; Igros Kodesh of Rebbe Rayatz; Divrei Sofrim p. 270; Mishneh Halachos 6:230; Az Nidbaru 6:50-6; Ach Tov Leyisrael [Kachlon] 2:17
Other opinions: The Chachamim rule that it is permitted for two single men to be alone together and to sleep together with the same sheet. [Mishneh Kiddushin ibid, brought in Beis Yosef E.H. 24] The reason for this is because the Jewish people are not suspected to transgress Mishkav Zachur. [Kiddushin ibid; Rashi ibid; Beis Yosef ibid] Practically, we rule like the Chachamim regarding Yichud. [Michaber E.H. 24:1; Tur 24:1; Rosh Kiddushin 4:24; Rambam Issurei Biyah 22:2; Tosafus Kiddushin 81a; Rif Kiddushin 33b; Meiri Kiddushin 80b; Rashal Kiddushin ibid 31; See Gan Hamelech 61] Accordingly, some Poskim rule that even today there is no prohibition for to men to sleep together on the same bed, and we have never heard of anyone being careful in this. [Rashal Kiddushin 4:23 that one who is stringent against two males sleeping together with Kiruv Basar appears arrogant; Aruch Hashulchan 24:6 that Chas Veshalom we never heard anyone be careful in this; Possible implication of Bach 24 regarding Yichud and that the same would apply to sleeping together] Nonetheless, even they conclude that one who is stringent is blessed. [Aruch hashulchan ibid]
How can we rule against the Chachamim? This is seemingly due to two reasons: 1) In our generation there is greater challenge in this field of Mishkav Zachur, and therefore one must be Machmir like Rebbe Yehuda, even though in general we rule like Chachamim. [See Michaber ibid] b) Perhaos even the Chachamim were only lenient regarding sleeping with the same sheet on two different beds, or on the ground. However, to sleep together on the same bed, is more severe.
 The reason: As this can lead to Mishkav Zachur. [Rashi ibid; See Daas Kohen 3 for a Maaseh Shayah] Or sinful thoughts, even though it will not lead to Mishkav Zachur. [Nidchei Yisrael 24]
A Maaseh Shehayah: Many years ago I [the author] had a conversation with an individual who struggled for many years with homosexual thoughts and he said that it began with a Yeshiva camping trip in which the boys slept together in tents. There were two boys per tent, and the tents were small, and he and his friend slept with the same sleeping bag. This awakened within him a homosexual Taavah for the first time, and from that camping trip and on he had to battle this Taavah for many years, until through therapy he was able to overcome it. He never sinned due to this Taavah, and is today happily married with children. This story is not an isolated incident, and the warning of the Poskim should be taken very seriously, as even if it does not lead to actual sinful activity between the two parties at that time [which indeed seems far-fetched], it can enter these feelings into the hearts of the individual and cause him decades of unnecessary pain and suffering! וד”ל ואין להאריך בדבר שהצניעות יפה לו והארכנו כבר די והותר וכל מי שיש לו מוח בקדקדו ויודע מצב הדור מבין חשיבות הענין
 Beis Shmuel ibid; Chelkas Mechokeik ibid
 Shelah ibid; Kaf Hachaim ibid
 Beis Shmuel ibid; Chelkas Mechokeik ibid; Tochachas Chaim ibid; Chofetz Chaim ibid
 See Michaber ibid; Toras Chaim [Shabsi] 3:1, and if that applied back then, then certainly today. וד”ל
The law in a generation that is not Parutz: Seemingly, it would be permitted for two men/boys to sleep together on the same bed if the generation is very refined and no Jews are suspected of Mishkav Zachar, as we rule like Chachamim. It seems, however, that we will need to wait for Moshiach to come for this question to become a anything close to reality.
 Michaber Even Haezer 21:7; Beis Shmuel 21:14
If they are undressed-Contradiction from 73:3 regarding Shema: Michaber and Admur 73:3 imply that it remains permitted to sleep together unclothed even pass adulthood and the issue is only regarding saying Shema. This is in clear contradiction to Kiddushin ibid and Tur/Michaber E.H. ibid, of which the Michaber and Admur certainly does not argue on. This question is asked by the M”A ibid on the Michaber O.C. ibid and he concludes with a Vetzaruch Iyun Gadol. Several answers were offered by Poskim to differentiate between the cases in O.C. and E.H. [See Perisha E.H. 21 that in O.C. refers to case that other people are in room, in E.H. refers to Yichud with child; Elya Raba 73:5 that O.C. refers to father/son, mother/daughter; E.H. refers to Mother/son, father/daughter; See P”M 73 A”A 2; Machatzis Hashekel 73:2; Kaf Hachaim 73:11] It is however most perplexing that Admur ibid who saw the words of the M”A and most certainly the answer of the Elya Raba ibid or Perisha ibid but offered no hint in the text to an answer for this great contradiction; Furthermore, it is quite clearly implicit from the wording of Admur ibid that he refers also to a case of father/daughter and hence the answer of Elya Raba is negated. The only option is to say Admur holds like Perisha. If correct, then according to Admur it is permitted to co-sleep undressed when other people are around even when she is an adult. Vetzaruch Iyun Gadol, as concludes the M”A ibid! In conclusion, it is completely unclear to me as how Admur rules regarding co-sleeping irrelevant of Shema.
 Beis Shmuel ibid
 See Michaber 73:3-4 and Admur 73:3 who give one definition [i.e. age] regarding Shema; See Michaber E.H. 21:7 who gives a second definition [i.e. puberty and maturity] regarding co-sleeping without clothing
 See Beis Shmuel 21:14
 This is due to reasons of Chinuch, and extra Taharah, and to suspect that from age nine a boy can begin to develop
 See Nidchei Yisrael chapter 24
 Setimas Kol Haposkim; See Mishneh Zavim 4:1; Kesef Mishneh Mitamei Mishkav Umoshav 9:4;
 See Shabbos 65a “Avuha Deshmuel would not allow his daughters to esleep together”
The reason: While the worry of sin between two women is not on the level of severity as the sin of two men, nonetheless, practically, doing so can cause lesbian feelings to be aroused within a girl, and hence practically it is to be avoided not just in order to prevent sinful temporary thoughts, but also to prevent a possible lust from entering the persons heart which may take years to battle and overcome. וד”ל ואין להאריך בדבר שהצניעות יפה לו והארכנו כבר די והותר וכל מי שיש לו מוח בקדקדו ויודע מצב הדור מבין חשיבות הענין
 Written on 7th Iyar 5703 to Mr Nissan ??