(ABT 1517-ABT 1573)
+---Richard Trethewy (BEF 1550-)
+---Robert Trethewy (BEF 1575-DEC 1623)
| | +---William Hawkins
| +---Joan Hawkins 
(ABT 1530-)
+---Thomas Trethewy (ABT 1596-ABT 1664)
| +---Ann Burgess (-ABT 1637)
+---Robert Trethewy (AFT 1642-ABT 1690)
| | +---William Jolley
| +---Isabel Jolley (ABT 1606-)
+---Anthony Trethewy (ABT 1687-)
| | +---John Scawen
| | +---Trehane Scawen (ABT 1614-)
| | | | +---John Trehane
| | | +---Elizabeth Trehane
| +---Dorothy Scawen (ABT 1653-)
| | +---Gregory Arundell (-ABT 1653)
| +---Dorothy Arundell
| +---Edith Crane (-ABT 1666)
+---William Trethewy (ABT 1719-)
| +---Elizabeth Retallack
+---Henry Trethewy (ABT 1752-ABT 1800)
| +---Amy Buckingham
+---Robert Trethewy (ABT 1793-22 DEC 1874)
| | +---Hugh Hotten (ABT 1654-SEP 1733)
| | +---Melchizedek Hotten (ABT 1698-)
| | | | +---John Oliver (-AUG 1668)
| | | +---Thamason Oliver (ABT 1666-)
| | +---Hugh Hotten (-ABT 1787)
| | | | +---Richard Polgrain
| | | +---Grace Polgrain (ABT 1697-)
| | | +---Thomasin ?
| +---Grace Hotten (ABT 1756-)
| +---Mary Gummow
+---William Trethewy (ABT 1834-ABT 1871)
| | +---Cornelius Philp
| +---Mary Philp (ABT 1797-)
| | +---William Moore
| +---Mary Moore (ABT 1774-)
| +---Mary Benny
+---William Henry Trethewy (1860-16 DEC 1914)
| +---Sarah Bryant (1838-)
Henry William Trethewy (23 MAR 1896-26 APR 1983)
+---Jane Barry (-29 APR 1902)