For the Oath, I very much would like 'Fëanor's kin' to really be 'the Sons of Fëanor.' That is how they are collectively known, and that is who takes the Oath (Nerdanel, Celebrimbor, any random wives present - they are *not* involved in this oath-taking!) In Sindarin, that's easy: Fëanoriónath = the Sons of Fëanor (collectively).
In Quenya, I'm not sure.
yondo = son, so...Yondor Fëanáron? Yondor Fëanárova? Yondor Fëanárollo? Yondor Fëanáronen? No idea what case to use to indicate fatherhood. Genitive? Possessive? Allative? Instrumental? Or just Fëanároyondor?
Starting with Quenya that Tolkien wrote:
hildinyar = my heirs
tenn' Ambar-metta! = until world's ending!
vanimálion nostari = parents of fair children, or begetters of fair ones
Nai tiruvantes i hárar mahalmassen mi Númen ar i Eru i or ilyë mahalmar eä tennoio. = "may they keep it, the ones who are sitting upon thrones in the West and the One who is above all thrones for ever."
Vanda sina = this oath
Ah, got it!
Híni Ilúvataro “Children of Ilúvatar” Tolkien used the genitive to indicate the relationship between father and sons. So "Sons of Fëanor" would be
Yondor Fëanáro. Yondi Fëanáro?
Except, shoot, the
Litany of Loreto (1950s Quenya) uses '
Eruion' for "Son of God," specifically preferring this to a phrase starting
'Yón-'. So perhaps
Fëanároioni? That looks ridiculous. You can't really use a patronymic collectively.
anon (post-LotR) is another possible way of saying 'son' in Quenya, and is later than
yondo (which goes back to the 'Gnomish' stuff). But I'm not sure it 'stuck'?
Anoni Fëanáro?
I suppose we should use the version of the Oath found in Morgoth's Ring?
"Be he foe or friend, be he foul or clean,
brood of Morgoth or bright Vala,
Elda or Maia or Aftercomer,
Man yet unborn upon Middle-earth,
neither law, nor love, nor league of swords,
dread nor danger, not Doom itself,
shall defend him from Fëanor, and Fëanor's kin,
whoso hideth or hoardeth, or in hand taketh,
finding keepeth or afar casteth
a Silmaril. This swear we all:
death we will deal him ere Day's ending,
woe unto world's end! Our word hear thou,
Eru Allfather! To the everlasting
Darkness doom us if our deed faileth.
On the holy mountain hear in witness
and our vow remember, Manwë and Varda!"
Alternatively, there is the Lay of Leithian version:
"Be he friend or foe or seed defiled
of Morgoth Bauglir, or mortal child
that in after days on earth shall dwell,
no law, nor love, nor league of hell,
not might of Gods, not moveless fate
shall him defend from wrath and hate
of Fëanor's sons, who takes or steals
or finding keeps the Silmarils,
the thrice-enchanted globes of light
that shine until the final night."
or as Celegorm later recites it:
"Be he friend or foe or demon wild
of Morgoth, Elf, or mortal child,
or any that here on earth may dwell,
no law, nor love, nor league of hell,
no might of Gods, no binding spell,
shall him defend from hatred fell
of Fëanor's sons, whoso take or steal
or finding keep a Silmaril.
Those we alone do claim by right,
our thrice-enchanted jewels bright."
Obviously, a lot of concessions to make that rhyme in English (though worth pointing out that 'silmaril' rhymes with 'steal').