Related על קידושין 3:10

(Translating from Ehrfurt manuscript:) [If a man said to a woman:] "I betrothed you", but she says, "Only my daughter is betrothed"—the mother's relatives [that would be forbidden to him in the Torah if they were married] are forbidden [to him], but the mother is permitted to his relatives, he is permitted to the relatives of the daughter and the daughter is permitted to his relatives. "I betrothed your daughter", but she said, "You only betrothed me"—he is forbidden to the daughter's relatives, but the daughter is permitted to his relatives, he is permitted to the relatives of the mother and the mother is forbidden to his relatives.