Just cause I think this would be cute for the Finwëans (because large extended family yanno.) Bear with me, this needs a little context.
In my culture we don’t call older siblings by their names. More than respect, we do it as a form of endearment. For example, the oldest sister is ‘Apama’
Apa - Sister (affectionate)
Ma - short form of mother (also affectionate)
Another example is ‘Apajaan’, jaan as a generic term of endearment. Usually used for people you’re close to. This also applies to older cousins, especially first cousins who get the next closest endearments. Or if you only have brothers or only have sisters, they’d take the ones available.
Eg. I don’t have any sisters but I have an older female first cousin. I’d call her Apama.
Or maybe I don’t have any older brothers, so I call my male first cousin ‘Bhaijaan’ (Bhai = brother)
SO I think it would be super cute if our resident Aman born elves with their hundred names, also had these terms for their older siblings. It would probably only be used if there’s a significant age gap, so Mae and Mags would call each other by their names, Celegorm, Caranthir, and Curufin all use each other’s names.
All of Fingon’s younger siblings call him by an endearment. Argon also uses one for Turgon and Aredhel.
All of Finrod’s siblings call him by an endearment. Aegnor and Angrod call each other by names. Galadriel doesn’t because she wants to be Different TM but it comes out in moments of high emotion. Orodreth (because I like adding him even if it was one mistake in the official stuff) calls everyone but Galadriel by one.
Ambarussa use a big sister endearment for Aredhel, since she’s so often hanging Celegorm and they see her the most. And an older cousin term for Galadriel.
The Nolofinwëans and Arafinwëans use endearments for their respective older cousins, and those of similar ages, but only those still somewhat close to the Fëanorions use any for them once they leave for Formenos.
The exception is Maedhros and potentially Maglor (depending when he was born) as the first grandchildren with a larger age gap to the rest of the family. Everyone has to call them by some term, even if it’s just out of respect. Fingolfin and Finarfin ensured this out of love for the eldest kids.
Onto Finwë’s kids.
Fëanor is oldest so it doesn’t really matter. He doesn’t particularly care if the others call him by his name or anything else.
All of Findis’ younger siblings call her by an endearment.
Fingolfin and Lalwen are pretty close in age so they call each other by names mostly (we have some more generic equal terms too.) Fingolfin probably used something for Fëanor until pride took over both brothers.
Finarfin is the baby of the family and generally a ball of sunshine until they throw the crown at him. He calls everyone by something, including Fëanor because let’s face it. He’s probably old enough to be Finarfin’s dad by the time he’s born 😂
Now the interesting thing would be seeing how these relationships dissolve over time, and when they lose these terms of respect or endearment. When the younger members start calling their siblings or cousins by their names instead. Because I don’t think it would change just because of a new language.
Most of them start calling Maedhros by his name only after the first kinslaying and Helcaraxë. Some of them return to calling him by an honorific when they see what Morgoth did to him and he gives up the crown to keep peace.
They all stop calling the rest of the Fëanorions anything but their names though. The exceptions are Fingon (who only used one for Maglor other than Mae, and that was more out of general affection than because he was older) and Finrod.
Finrod has one for Celegorm as well (he is in fact a bit younger) which he uses until the Nargothrond situation because listen. I sincerely doubt Finrod would’ve just let Celegorm and Curufin in freely if he didn’t have a good relationship with them.
Turgon starts calling Fingon by name sometimes after losing Elenwë. He doesn’t know why, he shouldn’t be angry at his brother… but he doesn’t have anywhere else to take out his fury. Fingon’s heartbroken, but he understands.
No one calls Turgon anything but his name after his disappears. Ironically enough Turgon starts calling Maedhros and Fingon by theirs again once he moves away.
Depending on their mood, the twins do or don’t call Aredhel by hers. They don’t blame her exactly, but it hurts that she’s gone. Then again, it’s not like they don’t deserve it after the boats. The younger Arafinwëans are a little less forgiving.
All the younger Fëanorions and Nolofinwëans call Angrod by name after the ban on Quenya. Some of them do the same to Finrod.
Galadriel completely stops using any and all terms after deciding to stay in Doriath. Catching herself even in those high emotion situations where it would sometimes come out. No one’s really surprised but it does hurt her brothers and Nolofinwëan cousins. She regrets this in the Second and especially Third Ages, and exclusively uses endearments when talking about them to keep some connection to her lost family.
Meanwhile on a faraway shore, Finarfin alternates between cursing his brothers and sisters’ names, and crying alone under still unfamiliar moonlight, calling for them in every term of endearment he can think of. They never answer.
…I’m sorry, this got kinda angsty towards the end 😂
Feel free to ask if you have any questions!