Pointing to a photograph, Bajpai said, "He is the son of the only daughter of…

Blood-relation puzzles are solved by decoding the sentence from the innermost phrase outward, fixing the gender and generation implied at each step, and then naming the resulting kinship term; when the speaker's own gender is not stated, the reading that matches one of the given options is the intended one.

1. "The father of my brother" is Bajpai's own father, since Bajpai and "my brother" share the same father.

2. "The only daughter" of that father is either Bajpai's sister (if Bajpai is male) or Bajpai herself (if Bajpai is a woman and her father's only daughter).

3. Testing the second reading: if that daughter is Bajpai, "he is the son of" her makes the photographed man Bajpai's own son, which would make Bajpai his mother — a relation that is not among the given options, so this reading is discarded.

4. Testing the first reading: with Bajpai male, that daughter is Bajpai's sister, and "he is the son of" her — so the photographed man is her son.

5. A sister's son is termed the brother's nephew; equivalently, the brother is termed the son's maternal uncle — and this reading's relation does match one of the given options.

Cross-check from the man's side: his mother is Bajpai's sister, and a mother's brother is always termed the maternal uncle — consistent with the chain above, and the only reading that lines up with an offered option.

Bajpai is therefore the maternal uncle of the man in the photograph.