It always bothered me that in the movies they made the characters from the Marauders era (Harry’s parents, Sirius, Lupin, Snape, etc.) so old. Don’t get me wrong, they are all played by great actors, but it has just always bothered me. I mean, part of the reason why Harry’s parents deaths are so sad is because they were SO young (only 22!). Also, Sirius was so much more relatable in the books because he missed out on alot of his life, and that’s why in his mid 30’s, he was still so immature. They shouldn’t have been that old.
I think Sirius and Remus have excuses for looking so old - being held in prison and constantly worrying about your affliction that prevents you from having a job or friends.
As for Lily and James, I’ve no idea.