Eomer, son of Eomund, main Marshall of Riddermark; and Theodwyn, sister of the king Théoden. Eomer`s father died when he is only 11 years old, soon after that his mother died also from grief .The care for him and her younger sister Eowyn take his uncle, Théoden which raised them like his own children’s. He has been always hated by king counsellor Grima, servant of Saruman, because Eomer is fight against the orcs which destroy lands of Rohan.

Later in the year of 3019 of Third Age he has news for band of uruk-hai which passes Rohan illegal. He breaks Grima orders to stay in Edoras and go to catch the group. In the back he found Aragorn, Legolas, Gimli which seek for there hobbit friends. Eomer with sorrow say they haven’t many chances because to found them alive because riders are burn the group of uruk-hai. He gives to them two horses, and after the end looking for hobbits invite them in Meduseld. After return of the Eomer in the halls of Meduseld he is arrested and released after Théoden healing.

Eomer fought alongside Aragorn at the battle of Helm's Deep. He rode along with his king to the Battle of the Pelennor Fields, and before Theoden died, Theoden named Eomer as the new King of Rohan. Eomer was also present at the Last Debate, and fought in the Last Battle before the Gates of Mordor.

After the War of the Ring, Eomer married Lothiriel, daughter of Prince Imrahil of Dol Amroth. He also formed a friendship with his uncle's former esquire, Meriadoc Brandybuck, that lasted until Eomer's death in forth age 63.