In Things Fall Apart, how is Ikemefuna similar to Okonkwo and his son similar to his father?

I'm not sure I understand your question. I'm not clear to whom "his son" and "his father" refer. however, I'll help you out as much as I can.

Okonkwo and Ikemefuna both represent virility and male gender roles among the Ibo. Generally, this means exhibiting physical strength. Ikemefuna earns Okonkwo's love and respect through his personality, which is always outgoing and upbeat, and his talents, which include identifying birds, trapping rodents, and making flutes. He knows which trees make the best bows and tells delightful folk stories. While Okonkwo doesn't approve of all these (anything having to do with music or stories he derides as "womanly"), he appreciates Ikemefuna for the change he has wrought in Nwoye.

Before Ikemefuna's arrival, Nwoye often incurred the wrath of Okonkwo. He considered his son weak and feminine, often treating Enzinma (his daughter) better than Nwoye (his son). Okonkwo saw too much of Unoka in Nwoye, and was terrified he would end up like his grandfather. Thus, Nwoye was physically beaten and mentally berated by his father. But when Ikemefuna arrived, Nwoye transformed. He became the son Okonkwo wanted, eager to hunt, grow yams, and scoff at stories as "children's stuff".

Although the conflict between Okonkwo and Nwoye informs many themes in the book, it is interesting to note that they are both alike in one way. They both stand apart from traditions and beliefs of the tribe. while Okonkwo does so in a violent and almost savage way, Nwoye does so by turning to the church. So while they move in two very different directions, their mutual separation from the tribe links them in their alienation.