Did Avraham really not know about his nephews while they were children?
After the Akeidah, Avraham returns home and then the torah tells us, in Bereishit 22:20: "Avraham was told, 'Milkah too has borne sons to your brother Nachor (etc)'". The torah does not always record events in the order they occurred, but in this case it's not the torah telling us about Milkah's descendants; the torah tells us that Avraham is being told this now, when some of those children are already old enough to have produced children of their own.
Was Avraham not in touch with, or aware of, his brother for several decades, that this was news to him? Or did he already know, but the point of him being told (reminded) now is that he's about to look for a wife for his son, and this is a reminder to look within that part of the family?
The torah does not tell us who told Avraham this. Rashi says that God told him and the specific point was to tell him that Rivka had been born, and Ibn Ezra also says that this is to tell us Rivka's lineage. But that doesn't help with the question of whether Avraham already knew about Milkah's children. Is only the announcement of Rivka new information to Avraham, or is all of it new?
The Ramban also asks how he could not know:
Now from the text of Scripture it would appear that Abraham had no knowledge of any of them except on that day. If they were visited with children in their younger days, it would be impossible for them not to have been heard until this time for the distance between Mesopotamia and the land of Canaan is not great.
And concludes that these children must have been born very late, after Avraham left Haran:
Now when Abraham left Haran he was seventy-five years old,393 and Nahor was also elderly and his wife too was not young.394 Indeed, we must say, G-d performed a miracle for them in that they were visited with children in their old age. This is the sense of the verse, Milcah, she also. In the words of our Rabbis, it is said395 that Milcah was visited with children as was her sister Sarah.
I don't understand how the second part I quoted addresses the first part I quoted, though. Even if these children were miracles of old age, the distances are not great (as he argued earlier). Regardless of when these children were born, it sounds from the text like Avraham was unaware of them even though at least some of them are adults already.
Did Avraham know about his brother's children earlier, or did he only learn about them after the Akeidah?