Why did Ishmael feel unworthy to go live with his uncle?

Nobody has ever been so kind to Beah. Later, Leslie brings Beah’s uncle to visit him at the center. The older man greets Beah with great affection and even begins to weep. Despite Beah’s protest that he does not know the man, Uncle Tommy replies “…we cannot go back. but we can start from here. I am your family and that is enough for us to begin liking each other”(p. 172). Beah’s uncle promises to visit every weekend and anticipates the day when Beah can return with him to his home to meet his aunt and their children. Beah is pleasantly surprised that his uncle keeps his word and visits every week; the two go on long walks and get to know one another.