Board Thread:Questions and Answers/@comment-33646122-20171224073704/@comment-38954730-20190328183223

Technically, they are not his sons, anyone ever wonder about their mother?

They never had one. Sans and Papyrus were grown in test tubes, sans first which is why he came out with a natural 1 DEF and ATK. Papyrus after, ironing out most of sans mistakes.

Feel free to argue.