Board Thread:General Discussion/@comment-26006155-20181123023529/@comment-26006155-20181123170232

Starscream1998 wrote: Just a question the whole 'parents age in relation to their child's development' is exclusive solely to Boss Monster's right? How old do you reckon all the other Monsters are? Yes Star, Gerson gives that bit of lore in the post-game dialog after the True Pacifist Ending.

If you go down to Gerson's Epilogue dialog, and click Show, then go to "Is Asgore a Goat?" You'll see the statement I'm talking about https://undertale.wikia.com/wiki/Gerson

Gerson is specifically talking about the nature of Boss Monsters here. And the only boss monster child that we know exists, at least at this point, is Asriel.