Tabi is Sonic/Xenophanes cause he'd be the most aggressive towards Boyfriend.

Skid is Tails cause he'd be the least aggressive towards Boyfriend.

Sans is Knuckles cause like how Knuckles is the guardian of the Master Emerald, Sans is the guardian of the Genocide run.

Papyrus is Eggman cause "Mwhahahaha" = "Nyehehehe."