Fëanor, Fingolfin, and Finarfin loved all their nephews and nieces I take no argument. They showed it in different ways, but there were never any malicious thoughts towards them.
Any competition they had was between each other (though Finarfin was very much youngest sibling literally cba to deal with his older brothers.)
Fëanor: Always has too much food, used to his kids bringing over their respective favourite cousin for a meal because they were out playing too late and he’s not exactly going to send a child home hungry. As they got older it was because they’d been out and this was the closest place to disappear away to and crash. He’s used to seeing various kids sprawled across the carpet in the living room, waking up with headaches and groans. He’ll never admit it, but he finds it hilarious and enjoys seeing the children happy. If his brothers ask? ‘What do you mean they were out, I’ve had your children here with me all night.’
Fingolfin: One day I’ll stop linking this post but I really like how it turned out so you get to see it again! Fingolfin happily lets them traverse his house, go through his belongings. He’s very much a partner in crime, helping them sneak around, acting as lookout. Pretending not to see a majority of sweet pasties disappear overnight. He lives closest to the busy parts of the city, so it’s not unusual for the kids to get ready at his house if they’re going out anywhere or even preparing for Court. Most of the kids have their own shared room, and they’re full to the brim of everyone’s clothes, jewellery, shoes. Essentially a whole wardrobe. It gets messy, but he loves seeing his house full of life. Even if he could do without the mess Tyeko and Iressë bring in… and the various musicals at 3am. ‘You know we never tire of having you here… but perhaps you could tone down the partying? Just a little?’ He wouldn’t have it any other way.
Finarfin: My guy ofc has his house by the sea which like Fingolfin’s, has many many rooms full to the brim with clothes and jewellery. It’s essentially a home away from home for his niece and nephews, they don’t have to pack because everything’s already there. As youngest uncle and closest in age, he’ll just so happen to tell the kids where to have fun. He had the least pressure on him growing up and knows the best places in Tirion and Alqualondë. Going to Finarfin’s is like going on holiday, he’ll back them up and make sure they can do what they want without worrying about their reputations as princes and princesses. ‘The kids are far too stressed and don’t get to come here often, brothers. Let them have their fun. I’ll take care of them.’
Bonus!
Finwë: The mastermind. The accomplice. The alibi. He has a wild side to him born in Cuivienen and honed over the Great Journey. Court life is too stuffy even for him sometimes, let alone his grandchildren. He’s the one telling them all the wild things he got up to in his youth with a wink at the end subtly telling them how to do things their parents definitely would not approve of. High King Finwë would never! High King Finwë definitely would, and he’s making sure his grandkids get the experience too. He’s the one who gets the parents to leave for weeks at a time and his grandchildren have the time of their lives. ‘My sons, you worry too much! Don’t you trust your father?’