Assertion: It mentions Girushin [unnecessarily] along with death. Even if she was divorced several times, she may remarry.

Implied question: Why couldn't we say that it mentioned his son for a Chidush? Even though R. Yehudah forbids Anusas Aviv [we permit the son. We are not concerned lest the father fulfilled his plot, and was Mezaneh with her!]

Answer: This would explain "their sons". However, why does it say "their brothers", if not to infer that the father is forbidden?

Reference: I explained this above (18a), and will explain further in the Gemara (27b) regarding the argument of Rav and R. Yochanan.

Explanation #1: Granted, if you will say that Yesh Zikah, we understand why it mentioned four, to teach that Yesh Zikah even when there are two [Yevamim];

However, if Ein Zikah, and the reason [Yibum is forbidden] is due to Bitul Mitzvas Yevamin, the Mishnah should teach the case of three brothers;

It is a bigger Chidush that it is forbidden to be Mevatel [Mitzvas Yevamin] even though one of the Yevamos is not proper for Yibum (i.e. he can do Yibum only with one of them), and all the more so when there are four brothers, for then both Yevamos could do Yibum, one to each brother, it is forbidden!

Explanation #2 (Ri): We can say that now we are thinking that we are concerned for death of two brothers just like for death of one;

Therefore, we ask "if so, also three", since it does not come to teach the Chidush of the concern for death, since it did not teach five, which would be a bigger Chidush. (We forbid Yibum, lest the other two Yevamim die after one does Yibum.)

Rather, to teach the Isur of Bitul Mitzvas Yevamin, it can teach this even with three brothers!

Question: In Yoma (2a), R. Yehudah said "we even prepare another wife [for the Kohen Gadol on Yom Kipur], lest his wife die", and Rabanan asked "if so, there is no end to the matter!"

What is the difficulty? Here Rabanan are concern for death of one, but not for death of two!

Answer (Ri): They asked "since you are concerned for death in a short time, even though it is not common, you should be concerned also for death of two, even though it is not common. If so, there is no end to the matter!"

Citation (Yoma 13a) Answer: R. Yehudah holds that death of one is common, i.e. even in a short time. Death of two is not common.

Suggestion: There, Rabanan said that death is not common. This is because [if so,] there is no end to the matter!

Rejection: They say "[if so,] there is no end to the matter" because it is not common, like I explained, that death of one is common; it has an end. Surely, death of two is not common.

Alternate text: Some texts say "since you said that this one does Chalitzah to one, and this one does Chalitzah to one, you hold that Yesh Zikah."

Rashi's opinion: The text should not say this. It seems that he says so because also according to the opinion that Ein Zikah, this one does Chalitzah to one, and this one does Chalitzah to one;

We cannot do Yibum, due to Bitul Mitzvas Yevamin.

Suggestion: One should be able to do Chalitzah to both of them!

Rejection: Even according to the opinion that Ein Zikah, the Chalitzah Pesulah of Reuven, who already did Chalitzah to one of them, cannot uproot the stronger Zikah of Shimon.

Proof: Below, we say "granted, Rachel's Tzarah is not exempted, for Rachel's Chalitzah is Pesulah";

Inference: Even according to the opinion that Ein Zikah, the Chalitzah of Rachel does not exempt the stronger Zikah of her Tzarah, for we establish that Shmuel said this according to the opinion that Ein Zikah.

Similarly, the second Chalitzah of Reuven does not exempt her from the second brother, for we still did not think to distinguish between exempting herself and exempting her Tzarah.

Support (of alternate text - Ri): The text ("since you said that this one does Chalitzah to one... you hold that Yesh Zikah") is fine. The truth is, according to the opinion that Ein Zikah, an inferior Chalitzah exempts a greater [Zikah].

We explicitly say (below 51a) that according to the opinion that Ein Zikah, if he did Chalitzah to Ba'alas ha'Get (the Yevamah who received a Get), her Tzarah is exempted, even though Chalitzas Ba'alas ha'Get is more Pasul than that of the Tzarah.

Proof: She is considered a Chalutzah to him (the Yavam) to forbid him to her relatives;

Therefore, Shmuel, who says that if he did Chalitzah to the sisters, the Tzaros are not exempted; [if he did Chalitzah to] Ba'alas ha'Get, the Tzarah is not exempted, holds that Ein Zikah.

The Sugya just below is not according to the truth. Rather, it means that granted, Rachel's Tzarah is not exempted, i.e. even if you will say that also according to the opinion that Ein Zikah, a Chalitzah Pesulah must be repeated [with the other brothers].

Support: Now we understand why [even though] Rachel's Tzarah is not exempted, Leah's Tzarah is exempted, for it is a Kosher Chalitzah.

Proof: That Sugya is not according to the truth. We ask afterwards "is Rachel's Tzarah exempted?! A Mishnah says..."

Inference: We wanted to say that according to the opinion that Ein Zikah, Rachel's Tzarah is not exempted, even though the Tzarah is forbidden only due to her, and all the more so if they were equal.

Question: If so, how do we deduce even according to Rashi's text that Yesh Zikah, from the fact that we say that the middle one needs Chalitzah from both of them?

Answer: Rather, we cannot rely on that Sugya, like I explained, that we do not hold like the Sugya.

When we explain that Shmuel discusses whether he started or did not start [with the sisters], we no longer say that Shmuel said according to the opinion that Ein Zikah, like I will explain;

According to him, if he did Chalitzah to the sisters and to Ba'alas ha'Get, the Tzaros are exempted;

The text "since you said that this one does Chalitzah to one [and this one does Chalitzah to one], you hold that Yesh Zikah" is fine.

And since he said that the middle one needs Chalitzah from both of them, this shows that he holds that Chalitzah Pesulah must be repeated.

Implied question: We could have deduced both of these from the Seifa!

Answer: Even so, whatever we can deduce from the Reisha, we deduce from it!

Explanation #1 (Rashi): Whenever he cannot do Yibum, it is considered Chalitzah Pesulah.

Rejection #1: We said above (11b) regarding Machazir Gerushaso, that she or her Tzarah does Chalitzah, and Chalitzah of the [returned] divorcee is not considered Chalitzah Pesulah, even though he cannot do Yibum!

Rejection #2: Also below, we say that Leah's Tzarah should be exempted, for the Chalitzah is Kosher.

Inference: It is considered Kosher Chalitzah, even though it is forbidden to do Yibum, due to Bitul Mitzvas Yevamin!

Granted, he is not Mevatel Mitzvas Yevamin from Rachel's Tzarah.

Implied question: When he does Yibum to Leah, he will be forbidden to Rachel's Tzarah, just like the Tzarah of the relative of one's Chalutzah is forbidden!

Answer: Even so, mid'Oraisa she needs Chalitzah, for she is not the Tzarah of Achos Ishah after he does Yibum to Leah, since already she was not Tzaras Achos Ishah from when her husband died;

When he does Chalitzah to Rachel's Tzarah, Leah is not forbidden, for one is permitted to the relative of Tzaras Chalutzaso;

Even so, there is Bitul Mitzvas Yevamin if he will do Yibum to Leah, for we are concerned lest Rachel's Tzarah die, and he is Mevatel Mitzvas Yevamin from Rachel.

Suggested answer (to Rejection #2): [We say that Leah's Tzarah should be exempted, for the Chalitzah is Kosher, only when] Rachel has many Tzaros, and we are not concerned lest all of them die. Alternatively, Leah did Chalitzah before Rachel fell to Yibum.

Rejection: If so, there was no need to give the poor answer "the Tzaros are not exempted" means the Tzaros of Rachel, and it says "Tzaros" (plural), i.e. whenever this occurs;

We should have established the case to be that they fell at once (i.e. Leah did Chalitzah after Rachel fell), and Rachel and Leah each have one Tzarah. Then, he may not do Chalitzah to Leah due to Bitul Mitzvas Yevamin!

Explanation #2 (Ri): Rather, Chalitzah Pesulah is only Achos Zekukaso according to the opinion that Yesh Zikah, Achos Chalutzaso according to everyone, and Ba'alas ha'Get and Ba'alas Ma'amar;

For all of them, the Zikah was weakened. Achos Zekukaso resembles Achos Ishto, who has no Zikah [at all];

Achos Chalutzah is like his divorcee's sister. Ba'alas ha'Get is like a Chalutzah, and Ba'alas Ma'amar is like one who did Yibum, who has no Zikah.

The same applies to a Sotah mid'Rabanan. The Yerushalmi calls this a Chalitzah Pesulah, regarding R. Shimon's opinion that Bi'ah [or Chalitzah with her exempts her Tzarah];

Also she is like a Sotah mid'Oraisa, who has no Zikah, for Tum'ah is written regarding her, just like Arayos.

Distinction: However, Machazir Gerushaso and [a Yevamah with whom Yibum is forbidden due to] Bitul Mitzvas Yevamin, the Zikah is no weaker, therefore it is considered Chalitzah Kesherah.

Question (R. Avraham of Borgveil): Why do we discuss three sisters? We can teach this Chidush even with two sisters, when they fell at once!

Each of them must do Chalitzah with both brothers, because Yesh Zikah, and Chalitzah Pesulah must be repeated with all of the brothers.

Answer (R. Avraham): There we can find that one of them does Yibum, for when he did Chalitzah to the second [to fall], the first is a Yevamah who was permitted, forbidden, and returned to her initial Heter She may do Yibum with the second brother;

Implied question: Also the second brother must do Chalitzah to the second [to fall], because her Chalitzah was Pesulah!

Answer: Even so, the first [to fall] is not forbidden to him due to Achos Chalutzaso, since the Chalitzah was only due to Chizur (repeating Chalitzah Pesulah with all of the brothers).

Source: This is clear from below (27b). R. Yosi b'Ribi Chanina asked R. Yochanan, who says that if the second [to fall] dies, the first is permitted, from the Mishnah which says that both of them do Chalitzah, but not Yibum;

Citation (27b) Question: What is the reason? Let one [of the brothers] do Chalitzah to the second [and the other can do Yibum with the first]!

Citation (cont.) Response (R. Yochanan): I do not who taught the Mishnah. (I cannot explain it.)

Rhetorical question: Why didn't he answer that she does Chalitzah, but not Yibum, because the latter needs Chalitzah from both of them, therefore the first is forbidden to both of them?!

Answer: Rather, surely she is permitted to the latter [who did not do Chalitzah first], since his Chalitzah was only for Chizur.

Rejection (Tosfos): This is not a proof. We can say that R. Yochanan did not want to answer this because he holds like Shmuel, who says that Chalitzah Pesulah does not require Chizur;

According to his (R. Avraham's) reasoning, he could have said that with two sisters, even the second [to fall] is permitted to the second brother [who did not do the first Chalitzah] after the first did Chalitzah;

Source: Rav does not distinguish between the first and second [to fall]. He says below that even if the first died, he is permitted to the second.

Rebuttal (Ri): Above (18a), it connotes that all, i.e. both the opinion that Yesh Zikah and the opinion that Ein Zikah, agree that both of them do Chalitzah, either due to Bitul Mitzvas Yevamin, or because she was once forbidden, like I explained above;

Only R. Yochanan did not know how to explain [the Mishnah of] sisters, and [he holds that] the first [to fall] may do Yibum.

Implied question: Why do we call her the middle? She is the last!

Answer: Each of the others does Chalitzah only with one brother, and this one does Chalitzah with both of them.

Implied question: Perhaps Rav holds that Yesh Zikah, and the case of the Shomeres Yavam (if she died, the Yavam may marry her mother - 17b) is according to the opinion that Ein Zikah?

Answer: [The Gemara] holds that this is unreasonable, for there (17b) we learn two matters - Ein Zikah, and in her lifetime it is forbidden due to Bitul Mitzvas Yevamin;

Therefore, we say that Rav himself holds like that teaching.