What is the ruling if a father and his son both have intercourse with the son's female slave in one period of purity, and she gives birth?
Chapter on What is Prohibited to Marry and Combining Between Them and Other Matters
Al-Mughni
Book of Marriage
Primary text
If a father and his son both have intercourse with the son's female slave in one period of purity and she subsequently gives birth, paternity is determined by the *qaafah* (the art of physiognomic judgment). The child is ascribed to whomever the *qaafah* attributes paternity to, and she becomes an *umm walad* (mother of his child) to that person, identical to the ruling if only one of them had intercourse with her. If the *qaafah* attributes the child to both of them, the child is ascribed to both.
Supporting text
If one of them subsequently fathers a child by her after the first instance, she becomes an *umm walad* exclusively to the first one, because her bearing the first child made her his *umm walad* due to his sole procreation, and the ownership status of an *umm walad* does not transfer to another person besides her owner.