Board Thread:Questions and Answers/@comment-27491885-20151228162741/@comment-26347196-20160106004910

Murderman21 wrote: I'm not sure just where I found this, but I've heard before that the two are fraternal twins, or brothers given birth to (or created) at the same time. Papyrus takes on the older brother roles of cleaning, cooking, and work. Sans is super lazy and adopts the role of little brother. I believe this is based on a fan theory that they are both created by Gaster. Buuuttt it's a theory, so I'd scratch that.