Marmadas Brandybuck was the son of Gorgulas Brandybuck and his mother's name is not known.
Born in 2943 3A, Marmadas had three children: Merimas (2981 3A), Mentha (2983 3A), and Melilot Brandybuck (2985 3A). On October 5, 2990 3A, Marmadas and his father fought in the Battle of Bywater against the Ruffians and their leader. Marmadas survived, but his father was killed in the fight. In 3001 3A, Marmadas attended Bilbo's Farewell Party with his family.
During the War of the Ring, Marmadas and his family joined the Shire Company under the leadership of Will Whitfoot to prepare for war against Sauron. Marmadas participated near the end of the Battle of Pelennor Fields where he slew down a couple of orcs that were retreating from the battlefield. He volunteered in gathering the wounded and carried them back to Minas Tirith. Later, Marmadas fought in the Battle of Morannon, giving Frodo a chance to destroy the One Ring. He was able to survive the ensuing battle, but Merimas and Mentha were slain which mourned him. Marmadas how his children fought with honor and valiance and gave them a proper burial in the fields of Pelennor. Marmadas and his daughter attended the coronation where Aragorn was made the king of Gondor.