His mother Margaret was the daughter of Sir Michael Stewart, 3rd Baronet, of Blackhall, Renfrewshire.
Dalkeith's father the 3rd Duke of Buccleuch owned the Drumlanrig estate in Dumfriesshire and had a strong influence in Dumfries elections.
However, Heron-Maxwell's chance did not come until the 1807 general election, when he was returned unopposed as the Member of Parliament (MP) for Dumfries Burghs.
[2] His daughter Jane Stuart Heron Maxwell (1806-1886) married John Shaw Stewart.
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