Introducing to a boy, Lata said, "His father is the only son of my…

In blood-relation puzzles, a person's father-in-law is the father of their spouse, so for any married woman, her own husband is one of the sons of her father-in-law. When she says a man is "the only son" of her father-in-law, she is directly naming her own husband, because no other man qualifies as that son.

1. Lata refers to "my father-in-law" — this is the father of Lata's husband.

2. She says the boy's father is "the only son" of that father-in-law.

3. Since Lata's husband is himself a son of her father-in-law, and the father-in-law has only one son, that only son must be Lata's husband.

4. Therefore, the boy's father is Lata's husband.

Cross-checking: the clue only links Lata to the boy's father through the father-in-law-to-son relation — it says nothing directly about Lata's own relation to the boy. So the relation to identify is specifically the one to the father, which the steps above fix as the spousal one.

Hence, Lata is the wife of the boy's father.