The elder said to the younger, Our father is aging, and there is not a man on earth to live with us in the customary way.
And they made their father drunk with wine that night, and the older went in and lay with her father; and he was not aware of it when she lay down or when she arose.
Then the next day the firstborn said to the younger, See here, I lay last night with my father; let us make him drunk with wine tonight also, and then you go in and lie with him, so that we may preserve offspring (our race) through our father.
The older bore a son, and named him Moab [of a father]; he is the father of the Moabites to this day.
1 Samuel 14:49
Now Saul's sons were Jonathan, Ishvi, and Malchi-shua; and the names of his two daughters were, of the firstborn, Merab; and of the younger, Michal.