Agatha is Jessie's aunt (the sister of his father) and is more well-to-do than the Bolliers. They turn to her in times of trouble, asking for small things, such as extra candles so that Jessie's mother can stay up late working on dresses. Since Jessie's father's death, Agatha has been irritable and withdrawn, and she is also fussy and demanding, telling Jessie how to walk and warning him not to be clumsy with her furniture whenever he enters her house. Jessie says, "I had no other memory of Aunt Agatha except as a woman who especially disliked me." Agatha dislikes the fact that Jessie makes a living playing the fife and tells him he should be apprenticed and learn a respectable trade, saying that she doubts he would gain any benefit from school. However, she is generous with her candles and other gifts, and although Fox never says this directly, the reader senses that Agatha does care about Jessie; She wants his life to be better than it is but can't express this wish in a positive way. When Jessie eventually returns from his long and harrowing journey, she treats Jessie with affection and kindness and no longer accuses him of being a "bayou lout."
Betty is Jessie's sister. She is four years younger than he and has little part in the story. She is quiet and kind, and he thinks of her often during the voyage. When he comes back, she is even nicer to him, treating him like an invalid. When he moves to Rhode Island, he sends for her and his mother and takes care of both of them financially.
Mrs. Bollier is Jessie's mother, a young widow who was originally from Massachusetts. She makes her living by sewing dresses for the wealthy ladies of New Orleans. One of the only beautiful things in their one-room home is her wooden sewing box, which has a winged fish carved on the top and beside which sits her basket of spools of bright thread. Jessie says, "By candlelight, the warmth of the colors made me think the thread would throw off a perfume like a garden of flowers." Sometimes, their home is filled with her work—rich swathes of damask or silk. She is harried and worried, always struggling to make enough money to feed her children. Even after Jessie returns from his voyage, his mother still sometimes weeps at the thought of what he has been through and at the thought of what happened to the slaves. Perhaps because of her Northern upbringing, she is against slavery. She warns Jessie to stay away from the market where slaves are sold and is shocked to hear of a slave called Star by her owner: "It's not a human name," she says.
Captain of the Moonlight, he is a ruthless man with a capricious temper, who, when he first meets Jessie, picks him up and bites his ear hard enough to draw blood, as a sort of warning about who's boss on the ship. His crew is afraid of him, although they know that on other ships there are captains who are worse. He lives in relative luxury on the ship, with private quarters, good food, and plenty of water, when the others do without, and he does not hesitate to flog Purvis when he is accused of stealing an egg from the captain's hen. He is single-mindedly devoted to profit and despises the anti-slavery British ships that run down slavers and confiscate their slaves and...