It looks like there’s more than one Captain John. Scandalous Charles can't be the father of Captain John of Westmoreland County, but he can't be ruled out as the father of a different one. Page 153 of https://www.jstor.org/stable/1915677?read-now=1&refreqid=excels...
John Ashton son of scandalous Charles petitions the court to divide his father’s estate…. “This John might possibly be the Captain John Ashton to whom John Aston of Stafford County left 20 shillings in his will dated September 6, 1682. It is certain this will could not have referred to Captain John Ashton of Westmoreland County who had been dead about five years when it was drawn up.”
The next page goes on to talk about “who the heck was Grace Ashton?” The 'wrong' Captain John Ashton's wife was named Grace. That wasn't a super-popular name in those days, so it seems kind of unlikely that John Ashton son of Scandalous Charles would also have a wife named Grace.