Relatives are disqualified for eidus, as stated in Shulchan Aruch (Choshen Mishpot 33:2). This is true whether the eidim are related to each other – on the father’s or the mother’s side – or one of them is related to the chosson’s or kallah’s side. Although the mesader kiddushin must ascertain that the eidim are not relatives, sometimes an eid himself is not aware of his more distant relations, especially when they are through marriage, this is something to be careful about.
The following is a list of the eidim that are disqualified due to being related:
- Rishon b’rishon - Two people who are relatives of the first degree, e.g., two brothers or a father and son, are posul for eidus. This pesul is called “rishon b’rishon.”
- Sheini b’sheini - A “sheini b’sheini” also may not halachically be an eid. Thus, sons of two brothers, i.e., first cousins, are posul for eidus because of sheini b’sheini.
- Shlishi b’shlishi - However, two brothers’ grandsons, i.e., second cousins, are called “shlishi b’shlishi” and are kosher for eidus.
- Rishon b’sheini - A man and his nephew or a man and his grandson are posul as a “rishon b’sheini.”
- Rishon b’shlishi - The poskim argue about a “rishon b’shlishi,” e.g., a man and his great-nephew or a man and his great-grandson. Some say they are kosher (Mechaber); others say they are posul (Rema). It is proper to follow the latter opinion.
- Sheini b’shlishi - First cousins once removed are “sheini b’shlishi” and halachically kosher for eidus (Mechaber).
- Ba’al k’ishto - All pesulim for eidus also apply when that degree of relation is through marriage, since a man’s wife is like him, and a woman’s husband is like her. E.g., if one eid is a first cousin of the second eid’s wife, they are posul to serve as eidim together (Shulchan Aruch, Choshen Mishpot 33:3). People must be careful about this, as people sometimes do not know their cousins through marriage so well and can easily overlook this issue.
Machmir [Stringent] Even for Distant Relatives
Some are machmir not to use someone as an eid even if he is a distant relative who is not halachically posul (Sma, Seder Haget, ois 2). This is also so that people do not falsely claim that the marriage was made through related eidim. Many well-known poskim followed this (R’ Wosner, Kovetz MiBeis HaLevi Vol. 9, pg. 33; R’ Shach, Mevakshei Torah Vol. 27; Keneh Bosom; R’ Tuvia Weiss zt”l)
Revi’i b’revi’I - Because of this, some are careful not to use a revi’i b’revi’i, i.e., third cousins.
Chamishi b’chamishi - However, there is no reason whatsoever to be machmir for extremely distant relatives, e.g., chamishi b’chamishi [fourth cousins] or even rishon b’chamishi [e.g., a man and his brother’s great-great-grandson] (Kav Venoki).
