Solving the Relationship Puzzle
Let's break down the relationship described:
- "My father's wife" is the speaker's mother.
- "The only sister of my father's wife" refers to the speaker's mother's sister. This is the speaker's maternal aunt.
- "The daughter of the only sister of my father's wife" is the daughter of the speaker's maternal aunt.
The daughter of one's maternal aunt is their cousin.
Thus, the girl in the photograph is the speaker's cousin.