General Sahib

         In the novel The Kite Runner, General Sahib is Amir's father-in-law. He is also a good friend of Baba's, so there must be some kind of relation between them. It is possible, but not likely, that he may have know how Baba also had Hassan as his son. At the end of the book, the general refers to Sohrab as "the Hazara boy". It is possible that he too, like many others in Kabul, had a certain kind of dislike or discrimination against Hazaras. One piece of evidence that is given on this theory is when he walks in and sees Sohrab.

"'Hello, young man,' was all the general said, leaning with both hands on his cane, looking at Sohrab the way one might stud a bizarre decorative item at someone's house."

       It is obvious here that the general has a kind of racism against Hazaras.That much is clear. But it's what's in between the lines that is interesting. When I said that General Sahib might have known that Baba was Hassan's father, this may also lead to the general somehow knowing that Hassan had Sohrab. It is possible that Rahim Khan had talked to the general many times, and had also talked about Sohrab and how he was hoping to get Amir to take care of him. Therefore, when Amir and Soraya told him that they were going to adopt someone, the general assumed that it would be Sohrab. He then made up excuses for reasons to not adopt, because he didn't want a "Hazara" in his family. So when Amir came back with Sohrab, the general had no idea and assumed that Amir wouldn't adopt him. That is why he asked about Sohrab and why Amir brought him.
         Another part at the end was that the general had been summoned to Afghanistan. However, it could have been just a lie so that he could get away from Sohrab for a while. Or he was too embarrassed to be seen around him. Either way, the "summons" was probably a lie. My last assumption was that General Sahib was a Taliban. He may have hired Assef to kidnap Sohrab and make sure that Amir would not take him to America. He knew, or thought he knew, that Assef would not fail him, so the "summons" was to find Assef, and punish him for his failure.