The black sheep of the family means a person who can not mix well with other group members. In other words, one might have always different opinions from the rest of group members, which makes him very unique or feel alone. It also means that a trouble maker in a group.=  It also means a trouble maker in a group. Everyone is being good but a black sheep does some bad things which can be accepted in the group.= Everyone is being good but a black sheep does some bad things which can not be accepted in the group.