Pointing to a girl, Arvind said, “She is the daughter of the only child of my…

Concept

In blood-relation puzzles, first resolve every referential phrase — such as ‘the only child of my father’ — to one specific named person before assigning family roles. The word ‘only’ is a hard constraint: it rules out siblings, so the referenced person collapses onto the speaker's own identity whenever the speaker fits that description.

Application

Applying this to Arvind's statement:

1. Arvind refers to ‘the only child of my father.’ Since Arvind's father has only one child, that only child must be Arvind himself.

2. The girl is described as the daughter of that only child, i.e., the daughter of Arvind. So the girl is Arvind's own daughter.

3. The mother of a person's daughter is that person's wife. Since the girl is Arvind's daughter, her mother is Arvind's wife.

Cross-check

Cross-check with the family tree: father → Arvind (the only child) → girl, with Arvind's wife joining at Arvind's generation and linking to the girl only through motherhood — this confirms the relation independently of the verbal chain above.

Hence, Arvind's wife is the girl's mother.