Board Thread:General Discussion/@comment-27324545-20160105135410/@comment-32814756-20170809164459

I'd have to say:

frisk: 8

chara: 13

asriel: 10

toriel: almost over a thousand

sans: 13-14

papyrus: 8-12

undyne: not really sure, always seemed like a bratty teen, but from backstory perspective, i'd probably say 30 or 40

alphys: somewhere around 50 or 40.

mettaton - i would assume born around the 70s, since thats the era of entertainment mettaton's work is based off, so 40-50

asgore: a lot over a thousand

napstablook: probably younger than mettaton, since she always refers to him as 'blooky', and that's like a little brother name, so i would say 20

mystery man: as old as time. (thats just a fun one)

w.d. gaster: who knows. in the current realities that undertale is set in, w.d. gaster never existed, but if a gun was put to my head, i would say  75-100.

thats my opinion anyway.