Genesis 20:12-13

12But indeed she is truly my sister. She is the daughter of my father, but not the daughter of my mother; and she became my wife.

13And it came to pass, when God caused me to wander from my father’s house, that I said to her, ‘This is your kindness that you should do for me: in every place, wherever we go, say of me, “He is my brother.” ’ ”