Seeing that Franco is supposedly Jason's twin & Jason is supposedly AJ's brother & very close in age, I was bored & decided to look up a few birthdays.
For what it's worth:
Sean Kanan - AJ: 11/1966
Steve Burton - Jason: 6/1970 Yeah, it's possible. I don't know how many years apart AJ & Jason are supposed to be, but less than 3 years in real life sounds OK for casting purposes.
James Franco - Original Franco: 4/1978
Roger Howarth - New Recast Franco: 9/1968 10 years?!?!? We're talking recasting a 35 year old man with a 45 year old man. Nope, doesn't wash.
As for the 2 years older than his supposed twin, I suppose that is OK for casting purposes.
Bottom line, James Franco is the one who just doesn't fit into the age mix. Even before I checked birthdays, he always seemed way younger than Steve Burton. That was one loooooonnnnnnggggg childbirth.