Photograph puzzle: Pointing to a photograph, a man said, “I have no brother or sister, but that man’s father is my father’s son.” Whose photograph is it?

Introduction / Context:
This is a standard kinship riddle that hinges on the clause “my father’s son,” combined with “I have no brother or sister.” We must identify the person in the photograph.

Given Data / Assumptions:

• The speaker has no siblings.
• “That man’s father is my father’s son.”
• All terms are used in their usual, literal senses.

Concept / Approach:
With no siblings, “my father’s son” can only be the speaker himself. Therefore, “that man’s father is me.” Hence “that man” is the speaker’s son; the photograph is of his son.

Step-by-Step Solution:
1) Substitute: my father’s son = me (no siblings).2) Then: that man’s father = me → that man is my son.3) Photograph therefore shows the speaker’s son.

Verification / Alternative check:
If the speaker had a brother, “my father’s son” would be ambiguous (me or my brother). The explicit “no brother or sister” removes ambiguity.

Why Other Options Are Wrong:

• His own / His father’s / His nephew’s: None matches the derived identity “my son.”
• None of these: Not needed; “His son’s” fits exactly.

Common Pitfalls:
Treating “my father’s son” as someone other than the speaker despite the “no siblings” constraint.

Final Answer:
His son's