It appears that James Dundas (1734-1788), a Scot who settled at Philadelphia in 1757, was descended from no fewer than ten of the thirteen legitimate children of King Robert II of Scotland.
1. Robert III, King of Scotland.
2. Robert Stewart, 1st Duke of Albany.
3. Alexander Stewart, 1st Earl of Buchan (the "Wolf of Badenoch").
4. Isabella Stewart, m. Sir John Edmonstone, of Edmonstone.
5. Elizabeth Stewart, m. Sir Thomas Hay, of Erroll.
6. Margaret Stewart, m. John Macdonald, Lord of the Isles.
7. Joan Stewart, m. Sir James Sandilands, of Calder.
8. David Stewart, 1st Earl of Strathearn and Caithness.
9. Egidia Stewart, m. Sir William Douglas, of Nithsdale.
10. Jean (or Katherine or Elizabeth) Stewart, m. Sir David Lindsay, 1st Earl of Crawford.
I have never encountered a case of descent from so many siblings and half-siblings. Can any one match it?