the real reason that tim can't age over 18 is because if he did, dick would have an existential crisis about how old *he* is. wdym tim, who was 13 when dick met him, is 21 now. if tim has been doing this for 8 years, how long has dick been doing this for? wdym tim is legally old enough to drink now? if *that's* true then dick's no longer 25. when did dick suddenly get so close to 30. that's not a thing that's real. *his* annoying little brother isn't that old because dick's not that old. he hasn't really been working here for going on 20 years, right? can't be, because he just started here two days ago.
so yea, tim's not older than 17. who are you trying to kid here? dick's not gullible. he won't fall for your lies.
what utter nonsense are you going to try to tell him next? that damian's in high school or something? he's onto you.