Mary Weather Hargreaves

Cain's ten-year-old half sister. After her mother commits suicide to protect her from her obsessive suitor, Mary lives on the streets of London as a fortuneteller. Cain believes that she is his half-sister, and adopts her. Outgoing and strong-willed, she is often annoyed by Cain's relationships with women. She does not like how Cain shelters her, but accepts it because she believes that it eases his suffering. One of Cain's friends, Oscar Gabriel, becomes her self-proclaimed fiancé to win back his father's attention.


As the series progresses, he risks his life to protect her and she realizes that he genuinely cares for her. In the epilogue, she is married to him and pregnant with his child.

Although she is actually not related to Cain, he loves her regardless.
(Source: Wikipedia)