After these things, it was told to Avraham, "Behold, Milkah, too, has born sons to your brother Nachor.
The Torah tells us this story for a reason, it is not merely the background to Rivkah’s birth. The Torah writes that the two stories are inter-connected and that this story took place after the previous one.
The Ohr Hachaim explains that Yitzchok’s correct match was Rivkah, but only now, after the Akedah. After the Akedah took place, Yitzchok had more female characteristics than he should have, and that female soul had to leave him. When he underwent the Akedah, that Neshama left him and he was ready to get married.
However, the entire list of people who were born before Rivkah were unnecessary for this purpose. Nobody needed to know that they were born in order to tell us that Yitzchok’s match had been born.
The Ohr Hachaim explains that when a Tzadik is about to be born and his Neshama has to descend to this world, great Neshamos from the other side also descend to this world. All good in the world is enmeshed with evil, ever since the avera of Adam Harishon. When the good side arises, the badc parts of the world also awaken and has to be born. Rivkah was a Tzadekes, the mother of Klal Yisroel. When her Neshama had to descend to the world, all the evil in the world had to be born too.
