Naming one’s son or daughter after one’s father or mother while they’re still alive:[1]

Sephardim: The Sephardic custom is to name their children after their parents [i.e. the grandparents of the newborn] even during the life of the parents.[2] This is done out of fulfillment of the Mitzvah of honoring one’s parents, as naming one’s child after one’s parent is considered a matter of honor and respect. The Rebbe was accustomed to respond to people of Sephardic lineage that they may name their children after their living parents.[3] [This raises the question as to how this child is to be called by his parents, being that he shares the same name as their father or mother. Practically, if it is a common name, then according to all Poskim[4] the child may be called by that name while not in the presence of the grandparent, and according to most Poskim[5], the child may be called by that name even in the presence of the grandparent. However, Sephardim are to be stringent in this matter while in the presence of the parent.[6] If, however, it is an uncommon name, then the child may not be called by that name while in the presence of the grandparent[7], and according to some Poskim[8] should not be called by the name even not in the presence of the grandparent. Practically, Sephardim are to be stringent in this matter.[9] Accordingly, it is best for the child to be called by a nickname, such as Yossi instead of Yosef, in which case it is permitted according to all.]

Ashkenazim: The Ashkenazi custom is not to name a child after the father or mother of the parents [i.e., grandparents] while they are still alive.[10] [Likewise, we do not initially name a child after a great grandparent that is still alive.[11]] One may not swerve from this custom due to the potential danger involved.[12] The Rebbe was accustomed to respond to people of Ashkenazi lineage to not name their children after their living parents.[13]

Ashkenazim-If already named child: If one of Ashkenazi lineage already named their child after one of the child’s living grandparents then he should not change the name.[14] This especially applies if the name given is not the same name as the paternal grandfather.[15] This especially applies if the child has two or more names and only one of the names of the child are the same as the name of the grandparent.[16] Nonetheless, it is proper to call the child by the name that is not shared with the grandparent.[17]

[1] See Sheilas Shalom Tinyana 243; Sdei Chemed Mareches Chaf end of Kelal 104; Bris Avos 8:16;  Yabia Omer E.H. 7:7; Rashbash 291 in name of his grandfather the Ramban; Mahariy Asad Y.D. 247; Pesakim Uteshuvos 240:33; Toras Menachem 11:70; 5743 2:760, printed in Shulchan Menachem 5:160; Kuntrus Ziv Hasheimos 10; Shevach Habris 20:10; Nitei Gavriel 72:5

[2] Bris Avos 8:16; Sdei Chemed ibid; Yabia Omer 5:21; Rebbe ibid; Sefarim ibid; See Noach 11:26 that Terach named his son Nachor after his father who was alive at that time

The reason: This is considered to be a Segula for a long life for the father. [Bris Avos 8:16]

[3] Toras Menachem 5743 2:760

[4] Michaber and Rama 240:2; Rambam Mamrim 6:3; Ben Ish Chaiy Shoftim 2:4

[5] Shach 240:3; Derisha 240:4 [negated by Taz ibid]; Beir Sheva Horiyos, brought in Hagahos Rav Akiva Eiger; Chayeh Adam 67:8; Shut Haravaz E.H. 20; Yad Shaul 240:4; Zekan Aaron 2:60; Chakal Yitzchak 62; Igros Moshe Y.D. 1:133; Taz ibid negates this opinion

Other opinions: Some Poskim rule that in the same room as one’s parent, one may not call his child by the same shared name, whether the name is a common name or a rare name. [Rama 240:2 “However a common name may be called not in front of him”; Taz 240:5 and 242:4; Tur 240; Rambam Mamrim 6:3 [See Beir Hagoleh 240:11]; Ben Ish Chaiy Shoftim 2:4-5; Yalkut Meiam Loez Shemos 20:12]

[6] Ben Ish Chaiy Shoftim 2:4 that according to Maran it is forbidden and hence those who accepted his opinion must be stringent.

[7] Michaber and Rama 240:2; Taz 240:5 and 242:4; Tur 240; Rambam Mamrim 6:3; See Beir Hagoleh 240:10 that the Tur 240 as well as the Kesef Mishneh on Rambam Talmud Torah 5:5 and Hilchos Mamrim ibid wondered as to the source of the Rambam for this law; See Beir Sheva end of Horiyos [14a], brought in Hagahos Rav Akiva Eiger 240:2; Rashi Gittin 34b, brought in Pischeiy Teshuvah 240:3; Ben Ish Chaiy Shoftim 2:4-5; Yalkut Meiam Loez Shemos 20:12

[8] Implication of Rama ibid; Taz ibid

Other opinions: Some Poskim rule it is permitted to call a person by even an uncommon name, when he is not in the presence of the parent who shares the same name. [Derisha 240; Shach 240:3; Taz ibid negates this opinion]

[9] Ben Ish Chaiy Shoftim 2:4 that according to Maran it is forbidden and hence those who accepted his opinion must be stringent.

[10] Sefer Chassidim 408 and 460 and Makor Chesed ibid; Meishiv Devarim Y.D. 139; Darkei Teshuvah 669:1; Devar Eliyahu 37; Zekan Aaron 2:60; Yad Shaul 240:4; Mahariy Asad Y.D. 247; Bris Avos 8:16; Nitei Gavriel 72:5 footnote 7 in name of many Sefarim

The reason: Some write that this is in order to avoid the above-mentioned prohibition against calling another person by the same name as that of his father or mother. [See Poskim ibid] Others however negate this reason. [See Mahariy Asad ibid] Whatever the case, since we are particular in this, this itself brings on the danger of doing so and hence one must be careful in this. [Rebbe ibid]

[11] Igros Kodesh 3:181 discusses a case in which the child was named with the same name as his living great-grandmother, and the Rebbe is lenient for various reasons including the fact that the superficial language of the Sefer Chassidim 460 implies that the restriction only applies against naming after a living grandfather. Nonetheless, from this it is implied that initially one should not name the child after a living great-grandparent

[12] Toras Menachem 5743 2:760

[13] Toras Menachem 5743 2:760

[14] The reason: As the name of an individual is the channel through which his life and energy is drawn through and hence it is dangerous to change the name. [Toras Menachem 5743 2:760]

[15] Igros Kodesh 3:181

[16] Igros Kodesh, printed in Shulchan Menachem 5:1621

The reason: The reason for this is because the added name makes the entire name be considered a new name, and it is hence not considered that one is naming the child after the parent who has only one of the names. [Igros Kodesh 12:185; Tzemach Tzedek E.H. 173; 153 end of Vol. 1]

[17] Igros Kodesh 7:286; Letter printed in Shulchan Menachem 5:1621; Shevach Habris 20:12