(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
+---Henry Trethewy (29 OCT 1786-25 JUL 1871)
| | +---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
+---Alfred Hugh Trethewy (ABT 1832-02 AUG 1887)
| | +---Sampson Tresawna
| +---Jane Tresawna (ABT 1791-31 MAY 1875)
| +---Thomasine James (ABT 1771-)
+---Clement Robert Trethewy (06 APR 1873-01 JUL 1922)
| +---Mary Elizabeth Bidewell (ABT 1843-23 MAR 1920)
John Hugh Trethewy (1919-18 AUG 1942)
| +---Digory Truscott (ABT 1773-)
| +---Matthew Truscott (ABT 1810-)
| | | +---Matthew Quintrell
| | +---Jane Quintrell (ABT 1777-)
| | +---Catherine Cowling
| +---John Coad Truscott (ABT 1850-BEF 1916)
| | +---Elizabeth ? (ABT 1815-BEF 1871)
+---Ethelwin Truscott (ABT 1889-)
+---Clara Thomas (ABT 1856-)