All of them are sanses who lost alot from their timelines
Axe is a sans from Axetale he married frisk when she was in the underground and had a daughter named Aliza, frisk left the underground to get help but was raped and sent to insane hospital where she died and Aliza ran away to find Axe. After sometime Z-5 went through the underground, executing everyone but axe survived, he watched Horror and Gore die 
Tomb cares for Axe
Insane killed his papyrus and went insane, got hit and used DT on him