This family logic riddle says that a woman points to a boy and says, “His mother is my mother’s only daughter.” Who is the boy?
The answer is: her son.
The woman says that the boy’s mother is her mother’s only daughter. Since the speaker is a woman and her mother has only one daughter, that daughter must be the speaker herself. Therefore, the boy’s mother is the woman who is speaking.
That makes the boy her son.
The wording can feel confusing because it stacks several family relationships into one sentence. The easiest way to solve it is to identify “my mother’s only daughter” first. Once you realize that person is the speaker, the rest of the relationship follows immediately.


