black sheep 
noun informal
A member of a family or group who is regarded as a disgrace to it.Just suffice it to say that I have stood where you stand now - scorned by family members, labeled a black sheep....
- Would my beliefs make me the black sheep of the family?
- She is the black sheep of the family; drug rehab, shoplifting - you name it, she has done it.
Origin
Late 18th century: from the proverb there is a black sheep in every flock.