He was the third son of
Walter Stewart, 1st Lord Blantyre. Stewart was admitted to
Gray's Inn on 9 March 1620 when he was a
Gentleman of the Privy Chamber to James I. In 1624, he was elected
Member of Parliament for
Monmouth Boroughs but was unseated on petition on 28 March 1624 on the objection that he was a "Scotchman" and not naturalised. However he was re-elected MP for Monmouth in 1625 without further question. Stewart is also said to have been a qualified doctor. He left England in 1649 for France, where he was court physician to
Queen Henrietta Maria. He died in or by 1657. ==Family==