Scaramouche and Xiao both aren't human and are immortal, and they have plenty of things in common. Even if they're awkward and quiet, or if Scaramouche likes to annoy Xiao to the point Xiao snaps, they have got attached to eachother.

"Hey Xiao, your hair is a mess today. You look absurd." Scaramouche chuckled and then poked Xiao's cheek teasingly, while smiling affectionately at Xiao.