Genesis 19:35-39

And they made their father drink wine that night also: and the younger arose, and lay with him; and he perceived not when she lay down, nor when she arose.

Thus were both the daughters of Lot with child by their father.

And the firstborn bare a son, and called his name Moab: the same is the father of the Moabites unto this day.

And the younger, she also bare a son, and called his name Ben-ammi: the same is the father of the children of Ammon unto this day.