(ABT 1777-)
| | +---James Trethewy (ABT 1517-ABT 1573)
| | +---Richard Trethewy (BEF 1550-)
| | +---Anthony Trethewy (-JUN 1625)
| | | | +---William Hawkins
| | | +---Joan Hawkins 
(ABT 1530-)
| | +---Lewis Trethewy (AFT 1619-ABT 1693)
| | | +---Elizabeth ? (-ABT 1644)
| | +---John Trethewy
| | | +---Elizabeth Arundell
| | +---Robert Trethewy (ABT 1698-AUG 1771)
| | | +---Elizabeth ? (-JAN 1708)
| | +---Robert Trethewy (ABT 1725-BEF 1771)
| | | +---Grace Rogers (-SEP 1772)
| +---Elizabeth Trethewy (ABT 1748-)
| +---Mary Hill
+---Edward Trethewy (ABT 1799-)
| +---Ann ?
+---John Trethewy (ABT 1826-)
| +---Susanna Pinkham (ABT 1802-)
+---Alfred Trethewy (08 JUN 1862-)
| +---Esther ? (ABT 1828-)
William Claude Trethewy (11 MAY 1891-18 APR 1918)
| +---Thomas French (ABT 1814-)
+---Elizabeth Emma French (ABT 1862-)
+---Mary ? (ABT 1825-)