There is no clear definitive answer. There are quite a few people who think that Gaster is related to Sans and Papyrus in some way, usually as a father to the two, but the only evidence for such a position is that the "W.D" may (and to be fair, likely) refers to "WingDings," making a connection via the use of fonts as names. But another theory, which fits just as well, is that Sans and Papyrus are fragments of Gaster left behind when he fell into his experiment.
There's not really any way to specifically say that any given theory is right or wrong. We could point to the fact that Sans and Papyrus never mention having a lost brother, nor does anyone else mention a lost brother, but the same is true of Sans and Papyrus never mentioning having a father.
Mabian wrote: There is no clear definitive answer. There are quite a few people who think that Gaster is related to Sans and Papyrus in some way, usually as a father to the two, but the only evidence for such a position is that the "W.D" may (and to be fair, likely) refers to "WingDings," making a connection via the use of fonts as names. But another theory, which fits just as well, is that Sans and Papyrus are fragments of Gaster left behind when he fell into his experiment.
There's not really any way to specifically say that any given theory is right or wrong. We could point to the fact that Sans and Papyrus never mention having a lost brother, nor does anyone else mention a lost brother, but the same is true of Sans and Papyrus never mentioning having a father.
actually sans knows not papyrus cause papyrus realizes sans has a secret but he does not care sans keeps this as a secret
nah, i think sans and paps r the sons of gaster, the mother probably dying or something after having paps and gaster being lost in the void maybe after the skele-bros turn 16 or something seeing alot of comics out there that gaster was still there in sans and papyrus's baby and toddler days and maybe even in there mid and pre teens... but thats just a theory. a GAME THEORY.