Board Thread:General Discussion/@comment-30306971-20161023220253/@comment-27637436-20161112035206

It's a good theory, but there's a bunch of evidence the could lead to the fact that he's their father, or even related.

-Sans uses a Gaster Blaster, and If they're not related, why would it be called this, or even exist. (It appears Papyrus has them too, since in the 1.001 update, Papyrus says he would've "blasted" you if the Annoying Dog hadn't stole his special attack.)

-Their names are fonts (Wingdings, Papryus, Comic Sans)

-He looks like a skeletony-dude

-He fell into the core, and if you call Papyrus at the core, he says "THE CORE, YOU'RE GETTING CLOSE, HUH? ....", when those dots at the end appear, he has a sad/dissapointed face, meaning something happened here that he dosen't like.

-Sans' unused battle song, "Song That Might Play When You Fight Sans", has parts of "Gaster's Theme" in it.

That's all the evidence I've collected so far, so It's a possibility.