Ge 25:12 Now this is the genealogy of Ishmael, Abraham's son, whom Hagar the Egyptian, Sarah's maidservant, bore to Abraham.

13 And these were the names of the sons of Ishmael, by their names, according to their generations: The firstborn of Ishmael, Nebajoth; then 

16 These were the sons of Ishmael and these were their names, by their towns and their settlements, twelve princes according to their nations.

17 These were the years of the life of Ishmael: one hundred and thirty-seven years; and he breathed his last and died, and was gathered to his people.

18 (They dwelt from Havilah as far as Shur, which is east of Egypt as you go toward Assyria.) He died in the presence of all his brethren.

Moses is tracing the genealogy of Ishmael since he was Abraham's son too and he is showing here how God fulfilled His promise to Ishmael.

Ge 17:20 "And as for Ishmael, I have heard you. Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly. He shall beget twelve princes, and I will make him a great nation.