He was the brother of Faramir and the eldest son of Denethor II, the last ruling Steward of Gondor.
Boromir was honourable and noble; he believed passionately in the greatness of his kingdom and would have defended its people to the very last. Boromir's great stamina and physical strength, together with a forceful and commanding personality, made him a widely-admired commander in Gondor's army: he was made Captain of the White Tower, and quickly became Captain-General, also bearing the title High Warden of the White Tower. He was also heir apparent to the Stewardship. Boromir led many successful forays against Sauron's forces, prior to his journey north to Rivendell, which esteemed him greatly in his father Denethor's eyes.
Boromir was born in the year 2978 of the Third Age to Denethor II and Finduilas, daughter of Adrahil of Dol Amroth. His younger brother, Faramir, was born in the year T.A. 2983. The following year, Denethor became Steward of Gondor, succeeding his father, Ecthelion II.
After Finduilas' death in T.A. 2988, Denethor became sombre, cold and detached from his family. As their father withdrew, the relationship between Faramir and Boromir grew closer and greater in love. Denethor always favoured Boromir over Faramir, but this caused no rivalry between the two brothers. Boromir always protected and helped Faramir. Boromir was judged to be the more daring one, as well as the more fearless.
In response to prophetic dreams that came to Faramir and later to himself, Boromir claimed the quest of riding to Rivendell from Minas Tirith in T.A. 3018. His journey lasted 110 days, and he travelled through "roads forgotten" to reach Imladris, though, as he said, "few knew where it lay". Boromir lost his horse half-way along, while crossing the Greyflood at the ruined city of Tharbad where the bridge was broken. He had to travel the remaining way on foot. (Tolkien wrote of Boromir's journey that "the courage and hardihood required is not fully recognized in the narrative".)
Argonath RPG Community
Boromir, in the Argonath RPG Community, is also known as TeaM-MIB, one of the Community Leaders. He is currently the second Developer to use the name, after [R*]Kaltsu, the founder of ARPD and a semi-retired Developer.
Boromir is also a founder and one of the current leaders of TeaM MTA, one of the official Argonath RPG Clans.