I'm thinking maybe I can tie it in to his species somehow, like, their preferences or something.
As for species, last night I was thinking of making up a story about tigers who began to become to curious about the luxuries that humans had, and wanted them for themselves, so they made a deal with their goddess, but in return for the comfort and riches, they had to spend a few hours a day living as a human would, but the tigers didn't understand some human actions and occassionally murdered and such.
Idk. It's very raw and needs a lot more fleshing, but I think something similar would do well to explain both why Faint will act like a tiger occasionally, even when human, and why he and his family are wealthy and enjoy it so much.
I'm also going to talk it over with my friend who wants to get his sister and see if she has any good ideas.