Katherine of Aragon would NEVER acknowledge that a Pope and her parents erred in allowing her to wed her late husband's brother. (After all, she and Arthur never had sex.) The current Pope is never going to admit that a prior pope erred (papal infallibility, dudes). Henry should have offered to leave Mary legitimate as being born in a "good faith" marriage and allowed that Katherine might still (mistakenly) believe their union legal. Or make the same offer re Mary's legitimacy, but point out a son will make England safer (worked for French kings...). But, no, he's a mule and can't fathom anyone not agreeing with him. Ergo, we're still gonna have that annulment fight once Anne Boleyn is stalking into saying she won't 'do it' until they're legally wed.
ALSO: Catherine Carey was the child believed to be Henry VIII's bastard. Mary Carey's son was the YOUNGER of the two children she had with William Carey (I don't think Catherine was H8's - the family resemblance cited by everyone is the Boleyn/Howard resemblance - I've got a cousin who looks more like me than my sister.) H8's affair with Mary didn't come out until later - I still say if Katherine of Aragon had known about it, she'd have used it. I believe Henry wasn't sure it wouldn't come out (that he'd slept with Mary) and hedged his bets.
If you've seen portraits of Catherine's daughter Lettice, she looks so like a younger Elizabeth, I firmly believe that Catherine at least was Henry's. Not to mention that Henry did seek a dispensation to say he could marry Anne even though he'd slept with Mary Boleyn. He covered his bases, whatever really happened.