Board Thread:General Discussion/@comment-31344849-20170219160624/@comment-26185073-20170820183205

Mike202001 wrote: but GK is a gaster follower, and MK isn't. so does that mean that GK is the brother/sister of MK but is somehow involved with gasters experiments? GK is not a Gaster Follower. Goner Kid is not called such in the files, and does not act as one -- no mention of Gaster and you can use the phone in the room with GK.

It seems they literally do not exist. But since people theorize that Sans/Papyrus remember Gaster, why not Monster Kid remembering their sister?