Black sheep
(PW) a family member with a bad reputation
John’s way of life is so different from all of ours. He is known as the black sheep of the family.
(MW)
a disfavored or disreputable member of a group
(freedictionary)
n.
1. A sheep with black fleece.
2. A member of a family or other group who is considered undesirable or disreputable.
n
a person who is regarded as a disgrace or failure by his family or peer group
black sheep - a reckless and unprincipled reprobate
scapegrace, miscreant, reprobate - a person without moral scruples
(Wiki)
In the English language, Black sheep is an idiom used to describe an odd or disreputable member of a group, especially within one's family. The term has typically been given negative implications, implying waywardness.[1] It derived from the atypical and unwanted presence of black individuals in herds of white sheep.