Commentaire sur La Genèse 11:27

ואלה תולדות תרח, these were mentioned already in the previous verse, only Lot being added here. By adding the word תולדות, the Torah makes plain that grandsons, etc., are also called “offspring, תולדה of the older generation, not only their immediate fathers and mothers. This was especially so, seeing Haran died while his father Terach was still alive.

ויחי תרח..והרן הוליד את לוט. The offspring of Nachor is not mentioned, as Nachor did not beget any offspring until after the binding of Yitzchok on the altar in Genesis 22,20. Haran’s son Lot had to be mentioned as his son, seeing that Lot joined Avraham in his migration to the land of Canaan.