Study Guide Yevamot 44 The Mishna explains that if there are four brothers who all die childless, the oldest brother can do yibum with each of their wives. How can one marry four wives – isn’t that not financially responsible? One who has two wives, only one of them needs to do yibum or chalitza. From where is this derived? Why wouldn’t both be required? Why not just have one do yibum and the other chalitza? Rabbi Akiva holds that one who marries someone who is forbidden by a negative commandment, the child born from that union is a mamzer. The rabbis hold that only when it is a union that is punishable by karet. The example brought in which the rabbis agree that the child is a mamzer is the case of one who marries the relative of their divorcee. The Mishna mentioned that Rabbi Akiva said that one who marries the relative of their chalutza, the child is a mamzer. But isn’t that only forbidden by rabbinic law? A suggestion is made to change the text to the relative of their divorcee. The Gemara tries to find support from this from the wording in the Mishna but this proof is rejected. A different answer is brought to explain why Rabbi Akiva says the relative of his chalutza can create a mamzer, as it can be derived from the Torah. Rav Yosef said that all agree that the child born from one who remarries his divorcee after she married someone else in the interim is disqualified from marrying a kohen. Three questions are raised against this – two are answered but one is not. Therefore, Rav Yosef’s statement is emended to say that all agree that if a man marries a woman who is forbidden to him by karet, the child cannot marry a kohen. Who is “all” who agree according to Rav Yosef? This is derived from a kal vachomer from a widow.