While searching for something unrelated I came across a reference and a video about Elladan and Elrohir, Elven Princes, twin sons of Master Elrond or Imladris and Celebrian of Lothlorien, older brothers of Arwen. Tolkien recalls their birth in the year 139 of the Third Age, just a century before Arwen. The two princes will spend most of their lives between Rivendell (Imladris) Valley and the Elven kingdoms of Lothlorien. In the year 2509 their mother Celebrian is attacked by Orcs prompting the brothers to rescue her. In the attack she receives very serious wounds, then is taken back to Rivendell and healed by Master Elrond will however be leaving for the Undying Lands never to return. They appeared recently in fan-made movie inspired by The Lord of the Rings, Born of Hope.
Elladan and Elrohir will resent Orcs and hunt them wherever they were hiding for they were the cause of their mother's departure. During the War of the Ring, the Elven twins can be found in Rohan beside Aragorn, through all the major battles up to the final confrontation in front of the Black Gate of Mordor. It is at this point they make a brief appearance In Peter Jackon's adaptation in The Return of the King.
(pics from Born of Hope and The Return of The King)
After the War of the Ring, the brothers will remain in Imladris among mortal men even after their father's departure and it is not clear if they will be to remain here forever or depart as well for their final journey to the Undying lands - The last part of their story has been told in a short animated video made my fans Toby and Cody McClure , I hope you'll like it :)