Like the Boromir of The Lord of the Rings, the ancient Boromir was also a powerful warrior. It was while his father ruled Gondor that the race of the Uruk-hai first appeared, and Osgiliath was attacked and invaded. Boromir went to war and drove the enemy back from Ithilien for a while, but he sustained poisoned wounds in that war.
Boromir's Morgul-wounds wracked him with pain and shortened his life. He lived only seventy-nine years, a fraction of the usual lifespan for one of his line. When he succeeded his father, his Stewardship was to last no more than twelve years, but it paved the way for the historic rule of his famous and illustrious son Cirion.
Boromir ruled Gondor for twelve years, and was succeeded by his son Cirion.
The date of Boromir's birth appears only in The History of Middle-earth volume XII, The Peoples of Middle-earth. It cannot therefore be considered completely reliable.