Resumo
Filho de William Sinclair, 1º Conde de Caithness, 3º Conde de Orkney e Marjory Sutherland of Dunbeath
Irmãos (10)
1. Arthur Sinclair
2. Eleanor Sinclair, Countess of Atholl. Casou c/ John Stewart, 1st Earl of Atholl
3. Elizabeth Sinclair. Casou c/ John Stewart, 1st Earl of Atholl
4. George Sinclair
5. Katherine Sinclair
6. Margaret Mariota Sinclair
7. Marjory Sinclair. Casou c/ Andrew Leslie, Master of Rothes; David Boswell, of Glassmont, 2nd of Boswell
8. Robert Sinclair
9. William "the Waster" Sinclair, 2nd Lord Sinclair. Casou c/ Lady Christian Sinclair
10. William Sinclair, 2nd Earl of Caithness. Casou c/ Margaret or Mary Keith of Inverugie
Filhos (1):
- Oliver Sinclair
Casou c/ Isabella Levingstoun