I'd guess the Towers of Teeth
I am pretty sure I'm right. My answer is Carchost
Me and brother mine - Carchost and Narchost
by pure hearts we were born. - Built by Gondorians
Strong and tall we are - To keep anything from going into or out of Mordor
though darkess took us both. - they were taken by Sauron
Bearer of fire he - Narchost means Fire Fort
while I bear twice our name - Carchost means Fang Fort (carch = tooth, fang), and they were named Towers of Teeth
we stopped the men of fame - they stopped Frodo and Sam from going into Mordor, and the Host of the West
we're here to watch and see - they were used to keep an eye on that area
Me and brother mine - again
so much close we are - next to each other
but wall is between us - Black Gate
until the King's day comes. - when it was destroyed
good one btw !
