A little thought here. If reader has wings/feathers, and they're new to hell/heaven and don't know how to take care of them. And Adam or Lucifer(yeah i know that Valentino also has wings, but he doesn't have feathers so do not count) show reader how to preen them.
Like they notice that reader never does anything with their wings, and their feathers start looking dull and feel brittle. So, as a good caretakers that they are, they scold them for neglecting their wings, before showing them how to do it.
With Mourningstar i feel like he would do it right from the very start. Regular preening sessions.
Considering the ask, I'm adding another character here with Husk since he has feathered wings and would likely have to help Alastor's little in this situation.
Adam- is practically obsessed with looking his best as far as his wings go. He can get away with stubble or a bit of relaxed hygiene and general appearance upkeep since his mask and robes cover pretty much everything, but his wings are out there for anyone and everyone to see and they're almost a source of pride for him. After all, the first man has to have the most beautiful and pristine wings out of all the Winners, of course he isn't so vain that he would compare himself to say someone like Sera, buuuut he definitely spent more of his time ensuring that not a single feather was out of place.
So naturally his winged Litttle would need to follow his shining example. If they're Winners he's probably helping them from the get go if they struggle themselves because he can't be seen dead, or well, double dead, with anyone less than perfect and Winner Little goes wherever he goes, equal parts because of his trust issues and jealous/possessive nature. Will likely tease them at first when they struggle, and will scold them if they show absolutely no interest in the upkeep of their wings.
Now, Sinner Little would probably suffer for a bit. He's still very much pissed that he was saddled with a fucking Sinner of all people and hates that his Caregiver won't let him let you get exterminated by his girls. Plus, it's not like they're leaving the mansion so why the fuck should he care how they look? Only, the longer he's around them the more he does care, and eventually, maybe, he thinks they look pathetic enough, failing miserably to preen their undoubtedly itchy and uncomfortable wings that he takes pity upon them and takes mercy upon them and helps them out. Will likely insult their intelligence at first and say mean things along the lines of "you know the term filthy Sinner isn't meant to be literal right dipshit?" When he cares about them he might say sorry in varying ways and only ever apologizing sincerely when their asleep or farther into the future.
Lucifer, while not as clingy as Mourningstar, would likely still leap at the chance to help his Little. His scolding is mild at best if the Little shows no interest in preening themselves. He honestly would be secretly happy to be able to do this for them while also trying to help them do it on their own if that makes sense. Like he does want them to learn and grow as any Caregiver or parent would, but also if they never do in this aspect he is more than happy to continue doing these Daddy/ Duckling bonding sessions with them.
Mourningstar, however is actively infantilizing the everloving hell out of them as always. Preening was a regular part of their schedule from day one, if they attempt to learn to do it themselves he will merely chuckle and remind them with a soft smile that it's Daddy's job to take care of his babygirl and that he very much loves getting to do this for them, and they wouldnt want to make him feel sad and unwanted would they? As an added note, True Daughter would definitely use their wings as evidence they were related even if they looked nothing alike.
Husk, while not a Caregiver himself, I could see helping out Alastor's Little in the event they had wings and were unable to care for them properly. Honestly, if he noticed them struggling with preening or their wings were bothering them I could see him helping them learn on his own without Alastor using his soul contract to force him to. He's a surly alcoholic, but I imagine he has a soft spot for Littles and Pets especially.
However, Alastor would definitely enlist the cat's help the moment the Little's wings became unkempt enough to notice and he would likely give them a good scolding for letting it get this bad without telling him with a warning that next time they won't get away with a simple verbal lashing.
