Obi Umunna, Ona's father, never dominates the action of Buchi Emecheta's The Joys of Motherhood, yet his influence on his daughter is decisive. Through the claim he lays upon her, he shapes Ona's whole way of living and, indirectly, the destiny of her daughter Nnu Ego.
He binds her with the duty of an heir. Obi Umunna is a proud man of Umunna who has no son to continue his line. He therefore makes Ona, his only and much-loved child, promise that she will not belong wholly to any husband, but will bear a son to be named after him and to inherit his lineage. This vow is the single most powerful force in Ona's life.
He is the cause of her refusal to marry Agbadi. Because of her father's claim, Ona will not consent to become Nwokocha Agbadi's wife, even though she loves him and lives as his mistress. Her repeated refusals, which so wound Agbadi's pride, spring directly from her loyalty to Obi Umunna. Her father's wish thus governs the most important relationship of her life.
He shapes her proud independence. Obi Umunna has raised Ona to be spirited and self-respecting, more like a treasured companion than a submissive daughter. This upbringing helps make her the strong, wilful woman who insists on keeping her own will in a society that expects women to yield. Her celebrated independence is in part his making.
His influence reaches beyond his death. Even as Ona lies dying after childbirth, the tension between her father's claim and her love for Agbadi persists, and it is resolved only when she frees her daughter to belong to Agbadi's house. The struggle over lineage and belonging that Obi Umunna set going passes, like an inheritance, into the next generation, colouring Nnu Ego's own anxieties about children and continuity.
Conclusion. Obi Umunna influences Ona chiefly through the promise of an heir that he exacts from her. That promise dictates her refusal to marry Agbadi, reinforces her proud independence, and sets up the conflict over lineage that echoes into Nnu Ego's story. His quiet claim proves one of the shaping forces of the novel's opening.