Who is Christopher, Iphigene from I, Tituba, Black Witch of Salem and what is their importance?

Both Christopher and Iphigene are leaders of anti-white rebellions in Barbados. Both enter into sexual relationships with Tituba as she struggles to find a new place in her old homeland, both end up using and manipulating her, both end up losing their lives, and both are catalysts for important transformative events in her life. Christopher makes her pregnant, and Iphigene's involvement with both her and the rebellion eventually leads to her death.