John Stewart was born in . He was the eldest son of
Walter Stewart, 6th High Steward of Scotland, and his second wife, Isabel Graham. Stewart's father died in 1327, after which he inherited the lands of Ralston in
Cunninghame. Stewart may have begun his political career as early as 1344, as the recipient of a
charter from
David II of Scotland. He has been confused with his contemporary, John Stewart of
Dalswinton, who was captured at the
Battle of Neville's Cross in 1346. Stewart was associated with his elder half-brother,
Robert the Steward, amid tensions over David II's captivity in
England during 1352. He joined his half-brother at
Perth in 1364, when the latter performed
penance for failing to fulfill an agreement with the
Church to
legitimate his children. After becoming
King of Scots in 1371, Robert II appointed Stewart as
seneschal of the
Scottish royal household. Stewart held this office until 1377. His half-brother granted him an annual pension of
£20 in 1380, which he received consistently for the rest of his life. Stewart died in 1416, aged . ==Marriage and issue==