We know Beis Hillel and Beis Shammai had major machloksim about yibum to the point that perfectly valid marriages for one of them led to mamzerim according to the other. Yet the Mishnah still says that they didn’t stop marrying into one another’s families. The question is, does that mean because they respected each other’s psak, and therefore if Beis Hillel called someone a normal Jew, Beis Shammai would rely on that even though according to their logic he would be a mamzer? Or does that mean they respected each other to the point that even though Beis Hillel may have thought someone was not a mamzer, he would make sure to tell any Beis Shammai followers not to marry him because according to Beis Shammai he’s a mamzer? If it’s the second case, then if you are a talmid of R’ Willig or R’ Schachter, then of course you can use the pre-nup… just keep track to warn any potential R’ Elyashiv followers from marrying into that family.
Good point. Let’s read the gemara. Gemara says on 14b that they would tell each other which families they were not allowed to marry. So we’ll do that.