Mourad is more daring, and more adventurous than his cousin, Aram. Indeed, Aram says that "Mourad enjoyed being alive, more than anybody else who had ever fallen into the world," and also that Mourad had a reputation as "one of the craziest members" of the family. This difference is indicated at the very start of the story, when, at four o' clock in the morning, Aram is dreaming in bed while Mourad is outside riding a stolen horse across the fields.
Mourad is also a better, and perhaps more natural horse rider than Aram. Mourad is able to ride the stolen horse in "a fury of speed" which Aram describes as "the loveliest thing I had ever seen." Aram, on the other hand, can't control the same horse and is thrown off. Mourad says that he has "a natural way" with horses, and that horses "understand" him. Mourad's natural affiliation with horses also extends to other animals. Later in the story he heals the broken wing of a robin.
Mourad is also more assured and confident than Aram. When they initially lose the horse, Aram asks, "What will we do?" Mourad calmly replies that "we'll either take him (the horse) back or hide him." Later in the story, when the boys are confronted by the owner of the horse, John Byro, Mourad is the one who takes the lead and his self-assuredness seems to conciliate Byro. Aram, by contrast, doesn't say a word.
These differences between Aram and Mourad can be explained in part because of their different ages. Aram is nine years old, and Mourad thirteen. When Aram expresses that he would like to ride horses as well as Mourad, Mourad replies, "When you get to thirteen you'll know how to do it."