Elrohir is the son of Elrond and Celebrían, the twin brother of Elladan and brother to Arwen. They were born TA 130, which makes them about 2888 years old when we meet them in Lotro. The twins rarely part but fight wickedness together, fuelled by the memories of their mother's torment and that she left them early for the West. Elrohir and Elladan are so lookalike that it is hard to tell them apart, both dark-haired and grey-eyed. (Note: it is never stated who is oldest or that they truly are twins but that is inferred from Tolkien's fictional realm.) Elrohir is a Sindarin name for "Star-horselord".
At the latest it was in year TA 2933 they became best friend with Aragorn who that year lost his father, Arathorn. Then Elrohir and Elladan brought him under Elrond's protection and they soon adventured together. However, this friendship never broke the bonds with their father, some information was kept secret between father and sons, never to the bad though. The twins often rode with the Rangers of the North, rode scouting for their father, or carried important messages or information from him. They were somehow in contact with Strider (Aragorn) early on and they continue to support him in the quest of this tale. In future tales it will be Elrohir who brings Aragorn a silver horn so that he can summon the half-dead Oathbreakers. Never will Elrohir or Elladan hesitate nor exit a quest, rather Elrohir will say: "From the North we came with this purpose, and from Elrond our father we brought this very counsel. We will not turn back."
The tale does not tell the end of Elrohir's life, whether he chose mortality living with the Men of the new age, or whether he simply delayed his departure to the West joining his dear mother and father. We are told that he remains in Rivendell for the time being.
Elrohir will appear at different locations throughout this epic tale.
Elrohir (Thorin's Gate)
Together with Elladan he has arrived to the the area to explore the background of a curious dream their father told and he wanted to scout the tunnels for signs. Meeting him gives evidence of his wisdom and his superior expertise in herb-lore. Before and after this journey he is also involved in the High Elf intro and Prologue.
-  Intro (High Elf): Into Darkness Falls a Star
-  Intro (Dwarf/Elf): A Putrid Spring
-  Intro (Dwarf/Elf): Medicine of the Elves
-  Intro (Dwarf/Elf): To Evade the Impending Doom
-  Intro (Dwarf/Elf), Instance: Skorgrím's Tomb
-  Prologue (High Elf): Reflections of the Past
He and Elladan established this camp centrally within the Trollshaws. It is the base for the scouts who patrol the region, for Rangers and friendly visitors, and for many other purposes. Here Elrohir give directions and later he organises the upcoming journey of the Ring-bearer from here. During a skirmish Elladan also appears at The Ford of Bruinen.
-  The Sons of Elrond
-  A Scout in Nan Tornaeth
-  Return to Thorenhad
-  A Road Seldom Travelled
-  House of the Master
-  Down from the Mountains?
-  The Ford of Bruinen - Skirmish
-  Volume III, Book 1, Chapter 1: Gallant as Elf-lords
-  Volume III, Book 1, Chapter 2: Candaith's Hidden Cache
This far in the tale he and his friends are making the final preparations for the departure from Rivendell travelling southward. He is both worried about his father's curious and foreboding words, however determined to stand firm against the Enemy.
-  Volume III, Book 1, Prologue, Instance: Messages from Lórien - Solo only
-  Volume III, Book 2, Chapter 2: The Grey Company in Rivendell
-  Volume III, Book 2, Instance: As Near as May Be - Solo only
-  Volume III, Book 4, A Full History - Elf
-  Volume III, Book 4, Instance: The Rescue
-  Interlude: Many Worries
-  Retaking Pelargir