(Mishnah): A man was married to two orphaned minors, and died. If the Yavam had Bi'ah with one, and then he or his brother had Bi'ah with the second, he did not disqualify the first Yevamah;

The same applies [if the deceased was married] to two Chershos.

If a minor and a Chereshes [fell to Yibum], if the Yavam had Bi'ah with the minor, and then he or his brother had Bi'ah with the Chereshes, he did not disqualify the minor;

If the Yavam had Bi'ah with the Chereshes, and then he or his brother had Bi'ah with the minor, he disqualified the Chereshes.

(Gemara) Question: Even if he did not have Bi'ah with the minor, the Chereshes is forbidden [due to Zikah of the minor]!

Answer: If he did not have Bi'ah with the minor, and the minor died, he would be permitted to the Chereshes. Now that he had Bi'ah with [the minor], even if she died, the Chereshes is forbidden.

(Mishnah): If a Pikachas and a Chereshes [fell to Yibum], if the Yavam had Bi'ah with the Pikachas, and he or his brother later had Bi'ah with the Chereshes, he did not disqualify the Pikachas;

If the Yavam had Bi'ah with the Chereshes, and then he or his brother had Bi'ah with the Pikachas, the Chereshes is forbidden to the Yavam.

(Gemara) Question: Even if he did not have Bi'ah with the Pikachas, the Chereshes is forbidden [due to Zikah of the Pikachas]!

Answer: If he did not have Bi'ah with the Pikachas, and she died, he would be permitted to the Chereshes. Now that he had Bi'ah with [the Pikachas], even if she died, the Chereshes is forbidden.

(Mishnah): If an adult and a minor [fell to Yibum], if the Yavam had Bi'ah with the adult, and he or his brother later had Bi'ah with the minor, he did not disqualify the adult;

If the Yavam had Bi'ah with the minor, and then he or his brother had Bi'ah with the adult, he disqualified the minor;

R. Elazar says, we counsel the minor to do Mi'un.

(Gemara) Question: Even if he did not have Bi'ah with the adult, the minor is forbidden [due to Zikah of the adult]!

Answer: If he did not have Bi'ah with the adult, and she died, he would be permitted to the minor. Now that he had Bi'ah with [the adult], even if she died, the minor is forbidden.

(Mishnah - R. Elazar): We counsel the minor to do Mi'un.

Inference: This is b'Di'eved (after both had Bi'ah, we encourage Mi'un to enable the Yavam to keep the adult), but not l'Chatchilah (for one should flee from Mi'un, like we said above, 71a).

(Mishnah): If a Yavam and Yevamah are both minors, and they had Bi'ah, they may stay together while growing up;

If [a minor] had Bi'ah with an adult Yevamah, she stays with him while he grows up;

If within 30 days (of entering the Yavam's house) a Yevamah says that the Yavam has not had Bi'ah with her, we force him to do Chalitzah. If she says this after 30 days, we request that he do Chalitzah. If he agrees that he has not had Bi'ah we force him to do Chalitzah, even after 12 months.

If a woman vowed in the life of her husband not to benefit from her Yavam, we force the Yavam to do Chalitzah. If she vowed after falling to Yibum, we request of him to do Chalitzah;

If she intended for this [to prevent Yibum], even if she vowed in her husband's lifetime we request of the Yavam to do Chalitzah.

(R. Mana (in his own name), and R. Yitzchak brei d'R. Chiyah Kesuvah citing R. Yochanan): [Our Mishnah is] unlike R. Meir, for R. Meir says that one may not do Chalitzah or Yibum to a Ketanah, lest she be found to be an Ailonis. (R. Meir would separate them until both are adults, lest he is a Seris or she is an Ailonis, and she is Eshes Ach without a Mitzvah of Yibum.)

Ta'anas Besulim (a Chasan claims that his Kalah was not a virgin) is until 30 days. R. Meir says so;

Chachamim say, it is [only] immediately.

Question: What is the case?

If he had Bi'ah [with her immediately, all should agree that it is] immediately!

If he did not have Bi'ah [until now, all should agree that it is] even after a long time!

Answer: The case is Stam (he says that he had Bi'ah only now, but we do not know if this is true). R. Meir says that there is a Chazakah that a man can refrain up to 30 days, and Rabanan say that he cannot refrain even one day.

Question (R. Yirmeyah): According to R. Meir, is [a Yavam] believed to say 'I refrained for 30 days' in order to make the child a Shetuki? (I.e. she became pregnant, and he says that it is not from him. A Shetuki is a Safek Mamzer, for perhaps the father was a Mamzer.)

Answer: We learn from [what was said about our Mishnah]. If a Yevamah said within 30 days 'I did not have Bi'ah', we force him to do Chalitzah. After 30 days, we request that he do Chalitzah, and R. Lazar said that this is like R. Meir;

And R. Lazar said, this is only for her (since she admits that she did not have Bi'ah, she is forbidden l'Shuk without Chalitzah), but not for her Tzarah (the Tzarah is permitted due to the Chazakah that one cannot refrain);

Just like you say there, that [the Yevamah] is not believed to harm [the Heter l'Shuk of] her Tzarah, also here, he is not believed to harm his son (make him a Safek Mamzer).

If he said 'I had Bi'ah', and she said 'I did not have Bi'ah', even if he retracted and said 'I did not have Bi'ah', he is not believed, for initially he said 'I had Bi'ah';

However, if from the beginning [also] he said 'I did not have Bi'ah', both of them can uproot the Chazakah.