Suppose Reuvain & Shimon sign a document as witnesses for Levi. Now a few years later Reuvain marries Shimon's sister. Brother in laws may not be witnesses together. Rambam Edus - 13:6. Does this affect the document in any way Ex Post Facto?
see 14:5 [15ch]– Double AA ♦May 29, 2015 at 15:12
@DoubleAA: Why don't you post an answer?– Gershon GoldMay 29, 2015 at 15:19
The document would be unaffected, though hypothetically they may not be able to go to court together to testify on the validity of their signatures, as they would no longer be ne'eman to state "Zeh kitav yadi vizeh kitav chaveri." Instead, you would have a third party testify that the signatures are in fact from the eidim in question.– Isaac KotlickyMay 29, 2015 at 15:58
Shulchan Aruch Choshen Mishpat 46:35:
חתם בשטר עד שלא נעשה חתנו ונעשה חתנו הוא אינו יכול להעיד על כתב ידו אבל אחרים מעידים שמכירים חתימתו אפי' לא ראוהו עד שנעשה חתנו ויש מי שאומר דהיינו דוקא כשהשטר יוצא מתחת יד אחר אבל אם יוצא מתחת יד העדים לא:
If one signed a document before becoming a son-in-law [of the claimant] and subsequently became his son-in-law, he may not testify regarding his signature, but others can testify that they recognise his signature, even if they did not see it until after he became his son-in-law. Some say that this is specifically when the document is in someone else's hands, but not if it is in the hands of the witnesses.
הטע' משום דפסול קורבה אינו משום שחשוד לזייף אלא גזירת המלך הוא וכיון שחתם נעשה כמי שנחקרה עדותו בב"ד וה"ה בשטר ששני עדיו נעשו אח"כ חתניו או נעשו קרובי' זה לזה וכן הוא בתוספות ופשוט הוא:
The reason is because the disqualification of being a relative is not due to his being suspected of forgery, but is rather a 'decree of the King', and when he signed it is as if his testimony was examined in court. And the same holds true with a document where both witnesses subsequently became his sons-in-law or became related to each other. So is written in Tosafot and it is obvious.