Study Yevamot folio 10A with parallel Hebrew-English text, traditional commentary, and modern study tools. Free access to Babylonian Talmud online.
And your mnemonic to remember how this might occur is as follows: Died, was born, entered into levirate marriage, died, was born, entered into levirate marriage. In other words, there were several brothers, and one, Reuven, died, before another, Yissakhar, was born, and another brother, Shimon, en
§ Rather, R' Yehuda HaNasi does not hold in accordance with these general statements applied by R' Ḥiyya, and therefore he maintains that no issue subject to dispute was taught in the Mishnah. Rav Adda Karḥina, who was sitting before Rav Kahana, said in the name of Rava: Actually, one can explain
The Talmud elaborates: If Ya’akov, the father, raped two sisters who gave birth to two sons, and he had two other sons who married these raped sisters and died, in this scenario you find a case of her sister who is her sister-in-law, as there is a yevama who comes before one of the brothers who is
And if the father raped two unrelated women, who gave birth to two sons and then married two other sons of the same father who subsequently died, you find the case of: She who is forbidden to this one is permitted to that one, as each of the two raped women comes before one of the brothers for lev
§ Rav Ashi stated a different explanation: Actually, R' Yehuda HaNasi does not hold in accordance with these general statements of R' Ḥiyya, and the Mishnah does deal with halakhot that are in dispute. According to his opinion, what is the meaning of the phrase: It seems to me that he has no brain