Examine how Nnaemeka and his father are different.
One way in which both father and son are different from one another has to be in how each of them views tradition. Okeke is insistent that his son marry a girl of his choice. It is imperative to the father that the son adhere to the rules and traditions of the Ibo culture. Nnaemeka is fundamentally different in this regard. When he challenges his father's preconceptions in suggesting that he wants to marry a woman that he loves, the son shows himself as being different in his rejection of tradition. Nnaemeka displays that he is more willing to embrace his own freedom and choice than be submissive to whatever tradition dictates.
Another level of difference between them is their emotional flexibility. Nnaemeka is willing to embrace his father, even though he holds different beliefs about marriage. From the start of the story, the son seems flexible in trying to bring peace with his father. The son sends letters to his father and pictures, seeking to bring about consensus. This emotional pliability is fundamentally different from Okeke, who rejects his son with claims of "Satanic influence" or returning letters with Nene's had cut out of pictures. There is a fierce streak of stubbornness in the father that the son simply does not possess. It is here in which another difference between father and son is evident.