In The Namesake, Gogol struggles with his identity as an American-born Indian man. Even as a young child, Gogol is not in tune with his Indian ethnicity (he doesn't choose anything at his anaprasam, he chooses the very Russian Gogol as his name in school, he listens to The Beatles as a teenager, etc.) It isn't until after his father's death that he feels he should probably return to his roots and marries an Indian girl (Moshumi). At the end of the novel, Gogol starts reading the novel his father gave him, as a tribute to his heritage and his father.
Similarly in Drown, the narrator embodies the Dominican-American teenager living in the US. For many Hispanics, it is difficult to fully assimilate, the way Gogol had for example, without having your family call you out on it (they will think you are pretentious for denouncing your origins). The fact that he a fatherless teen always plays a huge role in identity since he does not have a positive role model to influence his actions or guide him in the right direction.