I am ashamed to say I didn't know who Feanor was. Or for that matter, do i know any more about him.
Feanor was the High King of the Noldor, his other name was Curufinwe.
Eldest son of Finwë, lord of the Noldor, and half-brother to Fingolfin and Finarfin, Fëanor was accounted the greatest of the Deep Elves. In Valinor, he captured the light of the Two Trees to make the three Silmarils. When Melkor stole these, and slew his father Finwë, he rebelled against the Valar and led the greater part of the Noldor into Middle-earth, swearing in the dreadful Oath of Fëanor that he would not rest until the Great Jewels were recovered.
On his return to Middle-earth, Fëanor immediately drove onward to Angband, though outnumbered greatly by Morgoth's Orcs and Balrogs. He was slain at last by Gothmog, the Lord of Balrogs, and such was the ferocity of his spirit that after his death, his body was consumed by flame.
And Legolas' hair colour might just be a matter of genetics. He describes himself as a Silvan Elf but the line of Thranduil (Legolas' father) comes down from Oropher who was a Sindarin Elf. Oropher came with a small band and merged with the Silvan Elves of Greenwood the Great and left behind their Sindarin inheritance. I don't think that any of the groups had a particular leaning towards dark or fair hair However you can't always leave behind genetic characteristics. Even with dark haired folk occasionally a blond haired kid will pop out! Just like
humans!
The term Silvan tends to be associated with woodland, because that's what it means. Silvan Elves settled in the woodland areas, so Legolas' folk and the Lothlorien folk were all theoretically Silvan.
Some of the Lothlorien Elves were Sindarin, some were Noldor and some were Silvan. Galadriel was Noldor, Celeborn was Sindarin. Although neither were actually Silvan Elves, they came to Lothlorien to rule after the Lorien Elves lost their King Amroth, who flung himself into the Bay of Belfalas searching for the maiden Nimrodel.
I would guess that if it were divisions of a real race of beings, then there would be inter-marriage between divisions anyway.
The divisions of elves into clans is below:
Avari
Calaquendi
Dark Elves
Deep Elves
Edhel
Eldalië
Eldar
Elves of the Light
Elves of the Twilight
Fair Elves
Golodhrim
Golug
Grey-elves
High Elves
Light-elves
Moriquendi
Nandor
Noldor
Sea-elves
Silvan Elves
Sindar
Teleri
Third Clan
Three Kindreds
Úmanyar
Unwilling
Vanyar
I'm full of absolutely trivial information!
