Board Thread:General Discussion/@comment-37639255-20190116122628/@comment-37979805-20190117185829

Actually, that's one of the more common Gaster theories out there. Other theories include Gaster being their brother or creator. I, personally, follow the Dadster theory, but I know people who thing Gaster is the brother of Sans and Papyrus. On Devaintart, a person by the name of zarla has a whole ongoing comic dedicated to the creator theory.

However, no matter which theory you follow, you can never know whether it's right or wrong, but the one thing we do know is that Gaster created the CORE.

Then, there are AUs. Let's not talk about them.