The practice of not marrying someone with the same name as one’s own parent—whether a bride with the same name as the groom’s mother, or a groom who has the same name as the bride’s father—is a tradition mentioned in the Testament of Rabbi Yehudah HaChassid (1150–1217).

In general, Rabbi Yehudah did not indicate the reasons for the customs and instructions he included in his will. Nevertheless, many communities meticulously follow his instructions, as he was a well-known Kabbalist whose instructions are taken to have mystical significance and are accepted at “face value,” so to speak.

Nevertheless, the concern is only when the exact and full Jewish names are identical (e.g. both mother and daughter-in-law are named Sarah Miriam). There is no concern at all if only one of the names is identical (e.g. Sarah Miriam and Sarah Leah). There is also no concern if only the civil names are identical, but the individuals’ Hebrew names are different.

This custom, in and of its own, is not a reason why to pass over a suitable prospective spouse. Rather, in an instance where the name of the bride or groom is the same as that of his or her future parent-in-law, a name can be added to the bride or groom (e.g. Yaakov can become Chaim Yaakov). This is done in the synagogue during the course of a public Torah reading; your rabbi can help you facilitate the naming.

I hope this helps,

Vidal Bekerman for Ask the Rabbi @ Chabad.org