Riddle- Geneology?!

Question:

Brothers and sisters have I none but this mans father is my fathers son? Who is this?

The ? is decieving!

Additional Details

2 weeks ago
Not quite- try again! I will provide answer-

2 weeks ago
First 3 are wrong...!

Answers:

The first speaker (who is a male only child) is referring to his son.

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