Genesis 19:33-38

So they gave their father wine that night, and the firstborn went in and lay with her father; and he did not know when she lay down or when she got up [because he was completely intoxicated]. Then the next day, the firstborn said to the younger, “Behold, I lay with my father last night; let us make him drunk with wine tonight also, and then you go in and lie with him, so that we may preserve our family through our father.” So they gave their father wine that night also, and the younger got up and lay with him; and again he did not know when she lay down or when she got up. Thus both the daughters of Lot conceived by their father. The firstborn gave birth to a son, and named him Moab (from father); he is the father of the Moabites to this day. The younger also gave birth to a son and named him Ben-ammi (son of my people); he is the father of the Ammonites to this day.