The genealogies of Esau (Gen. 36) show that his line produces many kings. This reminds us of the descendants of Ishmael in chapter 25, and perhaps also of the sons of Ham and the sons of Cain. The “other son” has the immediate success, while the promised line lives as a remnant.
Esau’s family heritage also shows that God has reserved a blessing for him. Whereas Isaac had no good word to give Esau, God proves himself the more benevolent father, as he indeed blesses Esau, just as he blessed Ishmael before him.