Would he? Possibly even probable. Did he? DNA says a man of his family did. So him or his brothers. Either is kind of skeevy. But saying that it was him for sure? Eh. Not enough evidence to be able to say for sure.
I know he freed other members of the family, like James who was Sally's brother and undoubtedly not his kid so saying that he freed them because they were his children also is something that is still a maybe.
The only reason the BS about his brother was dreamed up in the first place was to get Thomas Jefferson off the hook.