What did you get to know about the families of two boys from this story the beautifull white horse?

The two boys, Aram and Mourad, are part of the same family—they are cousins. Aram explains in the story that their family is part of the wider Garoghlanian tribe, which is extremely poor. He talks of the tribe as a family, and states that they were all notorious for their honesty, and had been "for something like eleven centuries." He goes on to say that the members of his family are proud, honest, and would not take advantage of anyone because of a strong sense of morality. This is why Aram goes to such great lengths to justify Mourad's stealing of the horse, because he does not believe any member of his family could be a thief.
We also learn that the family was considered to have "a crazy streak." Mourad is the youngest possessor of this crazy streak, which makes him the "natural descendant" of Khosrove, who is well known to be a very bizarre person. This sort of spiritual inheritance is considered more important than literal lines of descent in the tribe—the father of the "flesh" is not necessarily the father of a child's spirit.