A man looks at the photograph of a person X and says, She is the daughter of the husband of the only daughter of the father of my brother-in-law, that is my wife's brother. How is person X related to the man?

Person X is the man's daughter.

Brother-in-law is the wife's brother, and his father is the wife's father.

The only daughter of the wife's father is the man's wife.

The husband of the man's wife is the man himself.

X is the daughter of that husband, so X is the man's daughter.

Relation traced back to the man's own daughter.