Dang it! I was hoping like 20 or something. He does look in his 20s...
Presumably the same age as the actor - 45. It's hard for him to pass as much younger. If Daryl is supposed to be younger, I'd say 43 at the outside.
It never says for sure but I think he's meant to be in his late thirties, maybe even creeping into early forties. The actor that plays him is 45 if that helps?