Sister Boy is a prostitute working for Mama Mabel.
- "Sometimes pain is the only thing that gets them going. They can't do that to their wives, so they take it out on you."
- ―Mama Mabel to Sister Boy
Sister Boy was injured by a client and went to Mama Mabel to have her wounds treated. Mabel explained to her that clients would inflict pain on her because they could not do it to their wives. Mabel's grandson Cornell Stokes entered the room and Mabel chastised him for not being there to protect Sister. Stokes bitterly suggested that Sister should "learn to throw her hands up like a brother", for which Mabel angrily struck him.
- Sister Boy is the first transgender character in the Marvel Cinematic Universe.