He was a son of John Stewart of Bonkyll and father of John Stewart, 1st Earl of Angus.

He was the son of John Stewart, Prince Charles Edward Stuart's (Charles III) 'maestro di casa'.

Stewart was a younger son of John Stewart, 7th Earl of Galloway and his second wife, Anne Dashwood.

Robert was the fourth son of John Stewart, 1st Earl of Lennox and Margaret Montgomerie.

He was the son of John Stewart of Bonkyll and Margaret de Abernethy.

He was the son of John Stewart, 3rd Earl of Lennox.

Stewart was the younger son of John Stewart of Darnley and Elizabeth of Lennox.

He was a member of a junior branch of the family of the Earl of Galloway, being the first son of John Stewart of Castle Stewart.

He was the fourth son of John Stewart, 7th Earl of Galloway.

He was the son of John Stewart, 3rd Earl of Atholl and Grizel Rattray.