The Estermonts are one of the great families of the Stormlands, and are particularly prominent because Lord Estermont is maternal grandfather to the King Robert and lords Stannis and Renly. Lord Estermont is very old, and has many offspring, with at least two sons (Ser Eldon and Ser Lomas) and several grandsons and even a knighted great-grandson.
Ser Lomas Estermont and his son Ser Andrew are part of Stannis’s household on Dragonstone. Ser Andrew in particular had been Stannis’s squire for some years.
Lord Estermont, with his son Ser Eldon Estermont and Ser Eldon’s son Ser Aemon and grandson Ser Alyn, all followed King Renly until Renly’s death, when they then turned to Stannis. Ser Lomas Estermont and his son Ser Andrew were already following Stannis. After the disasterous defeat at the Blackwater, Lord Estermont was among those who was captured or changed sides and was presented to King Joffrey to swear his allegiance.
Ser Andrew Estermont was among the King’s Men who, with Lord Davos Seaworth at their head, helped to send Edric Storm to safety.