Leviticus 18:9-11

9Never have sexual intercourse with your stepsister, whether she is your father’s daughter or your mother’s daughter. It makes no difference whether or not she was born in your house.

10Never have sexual intercourse with your granddaughter, whether she is your son’s daughter or your daughter’s daughter, because she is related to you.

11Never have sexual intercourse with a daughter of your father and his wife. She is your own sister.