Who is Boromir's younger brother in The Lord of the Rings?

Boromir's younger brother in The Lord of the Rings is Faramir.

Both brothers are sons of Denethor II, the ruling Steward of Gondor, and Finduilas of Dol Amroth. Faramir is five years younger than Boromir. Their mother dies when Faramir is still a child, and Denethor openly favors the stronger, more celebrated Boromir, creating tension within the family.

Faramir serves Gondor as a captain and commands the Rangers of Ithilien. He first meets Frodo and Sam in The Two Towers, after Boromir has died. Although he understands the Ring's danger and feels its temptation, he refuses to seize it—a deliberate contrast with Boromir's moment of weakness.

Faramir survives the War of the Ring, becomes Prince of Ithilien, and marries Éowyn of Rohan. The films alter some details of his treatment of Frodo and the Ring, but his family relationship to Boromir remains unchanged.