Esther Trethewy 
| +---Philip Trethewy (-JUL 1733)
| +---Richard Trethewy (ABT 1720-)
| | +---Isabel Beaubery (-FEB 1732)
| +---Robert Trethewy (ABT 1759-)
| | +---Ann Jewell
| +---Robert Trethewy (ABT 1802-BEF 1861)
| | +---Elizabeth Sarah
| +---Richard Thomas Trethewy (ABT 1836-1908)
| | | +---William Trevithick
| | +---Mary Ann Trevithick (ABT 1808-1877)
| | +---Elizabeth Harry
| +---William Trethewy (1864-29 JUL 1927)
| | +---Elizabeth Coombe (ABT 1837-14 JUN 1919)
+---Gladys Trethewy (28 DEC 1897-10 MAY 1963)
+---Margaret Copeland (ABT 1868-07 NOV 1952)