Study Guide Yevamot 23 Presentation in PDF format Rabbi Yosi bar Yehuda derived from the verse “the daughter of his father’s wife” to exclude a daughter of a union of his father and a Canaanite slave or a non-Jewish woman from being considered one’s sister. The drasha is based on the word “wife” which seems to imply proper marriage. The Gemara questions why that case was limited, but others were not, such as, a sister born out of wedlock or from a prohibited relationship (either regular negative commandment, or one punishable by karet). In the end, only the non-Jewish woman is derived from the verse regarding the “daughter of his father’s wife” and a different verse is used to derive a child from a Canaanite slave. From where do the rabbis derive the law about a non-Jewish woman (since they use the “daughter of his father’s wife” to teach that one who has relations with his sister who is also his father’s wife’s daughter is punished double)? They derive it from the verse that says not to marry off your daughters to gentiles as they will turn your son (grandson) away. This is the verse from where we learn that a child’s Jewishness goes by the mother. That leads us to say that if a man has a child with a non-Jewish woman, the child is not Jewish and therefore not considered one’s sister. If a person betrothed a woman and isn’t sure if he betrothed her or her sister, he needs to divorce them both. If he died childless before he divorces her, his brother does chalitza to each. If he has two brothers, one does chalitza with one of the women and then the other can do yibum with the other. What if both brothers went ahead and married the sisters (one to each)? What if all these scenarios took place with two different men who each betrothed one of the women but do not know which one? The Mishna plays out all the scenarios in the previous case, but with two and has some more permutations as well. The Gemara tries to see whether we can learn something from our Mishna about whether or not betrothal is valid in a case where the man and woman are not permitted to have sexual relations with each other.