Cross reference
Genesis 25:16
16 these are sons of Ishmael, and these their names, by their villages, and by their towers; twelve princes according to their peoples.
Genesis 17:20
20 As to Ishmael, I have heard thee; lo, I have blessed him, and made him fruitful, and multiplied him, very exceedingly; twelve princes doth he beget, and I have made him become a great nation;
Genesis 17:23
23 And Abraham taketh Ishmael his son, and all those born in his house, and all those bought with his money -- every male among the men of Abraham's house -- and circumciseth the flesh of their foreskin, in this self-same day, as God hath spoken with him.