I have no firm evidence one way or another. The dates are a mess and I don't particularly count on these people to keep accurate track of their own age. It was a time when the calendar meant less and they weren't constantly confronted with paperwork asking for their age or their birthdate.
I think one of the men probably had children with a first wife who hasn't been recorded, but I don't know if it was Atkinson or Gwaltney. Or both of them even. It was the Gwaltney children who had the big gap in their ages so I assumed it was Gwaltney. But it's possible that somebody just simply screwed up the dates and there is no gap.
Here's something interesting: the Gwaltney family has a website about their family history. The page at http://gwaltney.faithweb.com/beginnings.html talks about the guy we're interested in. Thomas Gwaltney sails to America in 1635. Here's what happened next:
"Thomas Gwaltney ended up settling on the southside of the James River, and marrying a lady by the name of Martha Atkinson. Martha had previously been married to a Thomas Atkinson and had a son with him. So when Thomas married Martha, he also was bringing a step-son into his family. Around 1655, Thomas and Martha conceived a child, William, who was to carry on the Gwaltney name. Whether they had other children together is not for sure ( I have read where some thought he had a daughter named Nancy or Susannah). However, in his will, Thomas Gwaltney mentions no other children but William--perhaps because he had no other surviving children or perhaps because any daughters had been married off. By 1666, Thomas Gwaltney had died at the age of 53, and Martha Gwaltney ended up marrying a Thomas Pittman who now had the responsiblity of raising and educating young William Gwaltney."
Skipping ahead:
"But by July, 1666, Thomas was dead at only about 53 years of age. He left behind a wife, a young son William who was only around 11 or so years old, and the Atkinson step-son. Thomas' will was probated in September of 1666, and his widow, Martha, wasted no time--for in 1667 she found another Thomas to marry (she must have liked Thomases)--this time a Captain Thomas Pittman, who already had two sons about the age of young William Gwaltney. Of course, Martha herself died within several years, for by 1672, Thomas Pittman had remarried another widow, Lidia Judkins.
And young William Gwaltney was apparently the sole Gwaltney in the colonies with his 200 acre inheritance."
That's a lot less children than any of us expected, and I don't know where all the others came from. Gwaltney is an unusual last name so there probably weren't too many of them floating around. The family website has a couple of other pages on it dealing with other early family members and time periods, but I don't see anyone who fits our time frame.