Okonkwo and his son Nwoye have very few similarities, and they are all superficial. We could say that their similarities include being part of the same family, tribe, and village. The only other similarity the two share is that they both form a bond with Ikemefuna when he lives with the family. Ikemefuna is basically a hostage, turned over to Okonkwo's tribe after losing a battle to Umuofia. The boy lives with Okonkwo's family for three years, so naturally, he becomes like a son to Okonkwo and a brother to Nwoye. Both grow fond of their young hostage. The narrator says that "Ikemefuna called [Okonkwo] father" (28) and "he and Nwoye had become so deeply attached to each other" that Nwoye's inherent sadness begins to fade (34). Okonkwo actually begins to approve of Nwoye, a son with whom he has had a fraught relationship:
Okonwko was inwardly pleased at his son's development, and he know it was due to Ikemefuna. He wanted Nwoye to grow into a tough young man capable of ruling his father's household... (52)
Tragically, however, the Oracle eventually reveals that Ikemefuna must be killed. Ezeudu tells Okonkwo not to participate in this sacrifice because of his close relationship with the boy. To prove how unemotional and masculine he is, however, Okonkwo is the one to bring the machete down on his foster son.
This is the point where Nwoye and Okonkwo grow further apart. Nwoye's positive influence is gone, and there is now no buffer between him and his father's expectations. Nwoye is a quiet, sensitive boy, and Okonkwo is the quintessential manly man. Later in the novel, once the Christian missionaries come to Umuofia, Nwoye ends up converting, sealing once and for all his separation from his father. Nwoye is open to this new belief system and finds it appealing. Okonkwo, on the other hand, reveres tradition above all and rails against this development, even though he is too late (after returning from a seven-year exile) to do anything to stop it.
Ultimately, though they become closer due to their respective relationships with Ikemefuna, Nwoye and Okonkwo are polar opposites.