Alexander married Lady Mary Douglas, Of Queensberry in 1672 in Queensberry House, Edinburgh, Scotland. Mary (daughter of Earl James Douglas and Margaret Stewart) was born in Jan 1655 in Drumlanrig Castle, Dumfriesshire, Scotland, Great Britain; died on 5 Apr 1692 in Drumlembel, Campbelltown, Scotland, Great Britain. [Group Sheet] [Family Chart]

1. Sir John Stewart, 4th Earl Of Galloway was born in 1672 in Edinburgh, Midlothian, Scotland; died on 6 Apr 1741 in Derry, County Londonderry, Ireland.
2. James Stewart, 5th Earl Of Galloway was born on 16 Feb 1673 in Drumlembel, Campbeltown, Argyllshire, Scotland; was christened on 16 Feb 1673 in Campbeltown, Argyllshire, Scotland; died on 16 Feb 1746 in Glasserton, Wigtown, Scotland; was buried in Feb 1746 in Whithorn, Wigtownshire, Scotland.
3. Lady Henrietta Stewart was born in 1682 in Kilmacolm, Renfrewshire, Scotland; died on 21 Oct 1763 in Glasgow, Lanarkshire, Scotland.