Proving a negative is philosophically a very difficult argument to make, and in many cases is impossible. The onus would be on an historian to make a case that he did have children.
No one disputes that Moses had children. There is a record in Exodus, and a tradition. That Charlemagne had children is "proven" in that there are records of his children.
Proving that George Washington, for example, had no children is difficult. Saying that he had no legitimate heirs is simply a matter of saying, there is no evidence that he did. (Though with all the Claims, "George Washington slept here," doubtless some future historian is bound to say he bedded someone!). Proving that he had no children is only as valid as saying that no record of any progeny exists.
In the case of Jesus, there is zero evidence of any children, and zero evidence he was even married.
Because the record is so ancient, some might not consider that sufficient, however. That said, there being no evidence for, the only rational answer is to fallback on "you can't prove a negative." whilest completely true, it will nevertheless be unsatisfactory for those with an axe to grind. As such, I propose a more modern example of the same.
There is no evidence for George Washington having any children either, though I'm sure some mischievous person might choose to start a rumor. (don't believe me? Google 'Grover Cleveland' and ' Ma, Ma, Where's my Pa? Gone to the White House, Ha Ha Ha. )
In short, absent any kind of historical tradition or contemporary account (of which there is none) there is simply no way of sustaining such a claim.