Merrett Frey was the eleventh child of Lord Walder Frey of the Twins and grew up in the competitive and crowded castle where numerous factions plotted against one another, all encouraged by their father. Proving to have a skill for fighting, Merrett became a squire in the service of Lord Sumner Crakehall in the Stormlands. He served in Lord Sumner's campaign against the Kingswood Brotherhood, but did not fare well. He caught a pox from a whole, was captured by the outlaw known as Wenda the White Fawn and had a brand of a white fawn burned into his buttocks, ransomed back and then took a blow from a mace that nearly killed him and left him in permanant pain for the rest of his life. He took to drink to dull this pain. He married a daughter of House Darry and had four children.
Merrett was included in the conspiracy to carry out the Red Wedding and was assigned to get Greatjon Umber too drunk to effectively fight, although he failed in this task. He was later assigned to deliver the ransom for several lesser Freys captured by the Brotherhood Without Banners during the war, but, holding him as one of those responsible for the Red Wedding, the Brotherhood and Lady Stoneheart condemned him to death by hanging.
Merrett was the epilogue POV character in A Storm of Swords. He is the only epilogue POV character to appear in the series so far.