Both Joseph and George appear primarily as male objects of affection for Beneatha. While each of them have numerous distinct qualities, they are both young black men. During the course of the play, Beneatha distances herself from George and grows closer to Joseph.
George is African American and apparently well off. We do not learn his back story—in the sense of family history that led to his prosperity. His concerns are for class status, which he identifies with assimilation into dominant white society. Personally, he is overbearing and unpleasant in his interactions with Bennie, mocking her and criticizing her clothes and interest in Africa.
Joseph, who is from Nigeria, is a relatively new friend. As he knows Bennie from college, he seems to have a better grasp of her aspirations. He is heavily invested in teaching her about Africa and even more so in encouraging her interest in her heritage. The idea of her becoming a physician appeals to him, because he knows how great the need is. As the play ends, he proposes marriage and asks that she go to Africa with him.
Hansberry draws an unexpected contrast in that the American man has the more conventional gender expectations than the African man.