Yevamot

the same applies to five brothers also!  -The possibility that two might die  need not be taken into consideration. Rabbah  son of R. Huna said in the name of Rab: If three sisters who are sisters-in-law fell to the lot of two brothers who are their brothers-in-law, one of the brothers participates in her halizah with one, and the other brother participates in the halizah with the other, but the third,  requires halizah from both. Said Rabbah to him: Since you say that the third widow requires submission to halizah by both brothers, you must be holding the opinion that a Ievirate bond exists  and that the halizah is of an impaired character,  and that as an impaired halizah it must go the round of all the brothers;  but if so, [the same should apply to] the first [two sisters] also!  — If they  had become subject [to the levirs] at the same time the law would indeed have been so;  [the statement of our Mishnah, however,] was required only in the case where they become subject [to the Ievirs] one after another. When the first sister became subject to the obligation of the levirate marriage. Reuben  participated in her halizah;  when the second came Under the obligation. Simeon  participated in her halizah;  when the third came under the obligation.  if the one brother participated in her halizah he removed his own levirate bond,  and when the other participated in the halizah he likewise removed his own levirate bond. But, surely. Rab said that no levirate bond exists!  — This statement  he made in accordance with the opinion of him who maintains that a levirate bond does exist. Samuel, however, stated that one brother participates in the halizah with all of them. But consider: We have heard Samuel say that a proper halizah is required for Samuel said: