Board Thread:Questions and Answers/@comment-27491885-20151228162741/@comment-31333672-20170220205302

I would say Papyrus is the eldest, as he is a transformed Starman. The only way I could back this up is from the reference of the storekeeper, "Those skeletons showed up out of no where", meaning they are not originally from the underground, and Papyrus's armor. It is the symbol of the Starmen in EarthBound. Sans from what I gained, is a Psi user that used a time device, which destroyed his organic body. References of this are from the True pacfist run when you investigate San's lab.