"Zero Children" is the correct answer to this puzzle.
The given question is an interesting puzzle and we need to think logically. Implications are given.
Look carefully at the given words. "Yes" and "Yes".
The word "have" is used in the past tense to express past events.
The word "is" refers to the infinity of the present, indicating regular actions.
"HAD" is a thing of the past, but the question is about the current tension.
So, right now, Mr. Smith has no daughters or sons.
Therefore, the required answer is zero children.