This might be weird but how about Claude and Sebastian with an s/o who can actually talk to animals? Like, they can have an actual conversation. "Meow." "Really? Why?" "Meow!" "Hey, this young man says the master kicked him the other day and wants to know what his problem is." Or can tell what they actually need. "*Hiss*" "Yeah, she doesn't want to be touched right now, she says she's tired." Sorry, but I think it's so cool!
n’awww, this is cute!!
CLAUDE
This is perhaps an impressive ability for a regular human, but as far as demons go, this is among the tamer powers he’s seen. Of course, given that his S/O is technically human, he supposes he should act suitably impressed, shouldn’t he? He’s a little surprised that they’re able to do that; he truly has never heard of a human possessing any kind of supernatural power, and this qualifies as supernatural. One thing he wonders is if, perhaps, this skill of theirs extends to… say… spiders. If it does, he’ll be properly on board with it. Though he can somewhat understand spiders too, he’s very interested in hearing their every word.
SEBASTIAN
Oh, goodness… oh, what an incredible gift. This means he can understandwhat any beautiful feline is saying through his darling (Name). To everyone’s surprise (or perhaps not), he’s very enthusiastic about his S/O’s ability. It’s all he can do not to ask every moment what any cat he sees is saying to them. He also definitely holds conversations with cats now, using (Name) as a translator. One wouldn’t think someone like him would be so easily impressed, but when it comes to cats, he gets easily excited. He’s even more enamored of them now… plus, this power very likely infuriates Ciel, which is one more reason Sebastian loves it.