Agnes Steuart (1717-1778) (1717–1778) Parents Sir James Stewart, 1st Baronet Ann Dalrymple Children Henry Erskine David Erskine, 11th Earl of Buchan Isabella Erskine David Erskine, Lord Cardross Anne Erskine Thomas Erskine, 1st Baron Erskine Siblings James Steuart Joanna Steuart Anne Steuart Margaret Steuart Marion Steuart Partners Henry Erskine, 10th Earl of Buchan