The Major initially finds Abdul Wahid to be surly, but he soon realizes it's just the dude's nature. He's naturally serious. Maybe a little too serious and traditional and conservative, the opposite of his more liberal aunt, Mrs. Ali.
Despite being so conservative, Abdul Wahid had no problem getting an unmarried woman pregnant. He has a son, George, with Amina. Oops. When Amina comes to stay with Mrs. Ali, Abdul Wahid won't even sleep in the same place as an unmarried woman. Okay, he's not only crazy traditional, he's also crazy hypocritical.
Mrs. Ali enlists the Major to talk Abdul Wahid into marrying Amina. The Major lets Abdul Wahid stay with him, and in a very short period of time, he forms a more civil relationship with his houseguest than he has with his own son. Abdul Wahid leaves the place "wiped and spotless each morning" (14.76), too. He's the best guest ever.
The Major tells Abdul Wahid to be humble, relax his principles, and work on his "absolute arrogance" (14.111). This doesn't quite happen. Even when Amina's family gives the marriage their blessing, Abdul Wahid (rightly) fears that they're doing it only to gain economic advantage—you know, his aunt's shop. This would still compromise his precious principles, so Abdul Wahid decides to commit suicide on a technicality (he wants the wind to blow him off a cliff) to avoid everything.
It's up to the Major again, who is the strongest father figure Abdul Wahid has. And unlike the Major's own son, Abdul Wahid actually listens to him. The Major imparts a life lesson to Abdul Wahid, saying, "I was more proud of these guns than I was of your aunt Jasmina. For the sake of these guns, I let down a woman I love in front of a whole community of people, most of whom I can barely tolerate. I let her leave, and I will never get rid of that sense of shame" (24.109). In other words: dude, choose what's important.
Abdul Wahid chooses to marry Amina (after accidentally knocking the Major off a cliff and saving him), but Amina decides she doesn't want to marry Abdul Wahid, after all. Will these kids ever make up their minds? At least Abdul Wahid gets to see his son. Amina stays close, and we last see Abdul Wahid ruffling George's hair at his aunt's wedding.