Board Thread:Questions and Answers/@comment-31981697-20170724072306/@comment-33646122-20171230041842

some says that gaster adopted them after the war of humans and monsters and their actual parents killed in the war and theres a theory that they were created in the lab with an extract of human souls and some told me that their gaster's wife which is their mother was killed in the was so the existance of sans and papyrus is realy unknown