Bibike and Ariyike’s existence as twins appears in the earliest pages of Black Sunday. Later in the same chapter, Bibike explains how “Taiwo” and “Kehinde” are traditional Yoruba names to refer to twins. These names are used again and again through the novel, with both Bibike and Ariyike being referred to as Kehinde and Taiwo respectively—even when the other is not present.

The girls slowly grow apart throughout the novel. In the first chapter, they share the same feelings of worry when their mother loses her job; however, their paths diverge from there. Bibike teases Ariyike about her belief in the New Church. Bibike feels the separation when Ariyike admits to not liking Aminat. When Dexter asks Ariyike what she would change about her life, she replies she would not be a twin. In thinking this, Ariyike begins to understand her need for independence from Bibike. By the end of the novel, she will not have spoken with her sister in three years, but she will wonder if this consequence of her choices was worth it, suggesting the potential for reconciliation.

This motif is a useful tool for thinking about both Bibike and Ariyike’s character development.