Sans Papyrus Gaster has lots of abilities with Gaster Blasters, Bones, Teleportation, and are very good at combat
Lian has all of those abilities but both eyes glows blue when mad or serious
Gaster lost his wife, Arial a long time ago when they worked for the cops until the event and broke off from the police making their own Mafia while the Police leader (Asgore) his wife (Toriel) ran away with her son (Asriel) and made their Crime Ring and had some problems with the Skeleton family until frisk