(12 MAY 1835-25 NOV 1902)
| | +---James Trethewy
| | +---Richard Trethewy (ABT 1665-JAN 1741)
| | +---John Trethewey (ABT 1690-)
| | | +---Ann Martyn 
(ABT 1666-JUN 1738)
| | +---John Trethewey (ABT 1720-)
| | | | +---Phillip Mellow (ABT 1660-JAN 1711)
| | | +---Temperance Mellow (ABT 1690-MAY 1765)
| | | +---Jane ?
| | +---Richard Trethewy (ABT 1762-MAR 1836)
| | | | +---Joseph Grose
| | | +---Jane Grose (ABT 1724-)
| | | +---Jane ?
| +---Ann (Nancy) Trethewey (ABT 1807-)
| +---Ann Rickard (ABT 1779-)
+---William Trethewey (ABT 1876-03 SEP 1929)
| | +---James Trethewy
| | +---Richard Trethewy (ABT 1665-JAN 1741)
| | +---John Trethewey (ABT 1690-)
| | | +---Ann Martyn (ABT 1666-JUN 1738)
| | +---Joseph Trethewy (ABT 1735-DEC 1816)
| | | | +---Phillip Mellow (ABT 1660-JAN 1711)
| | | +---Temperance Mellow (ABT 1690-MAY 1765)
| | | +---Jane ?
| | +---John Trethewey (ABT 1764-JAN 1834)
| | | | +---John Rickard
| | | | +---Jonas Rickard (ABT 1705-)
| | | +---Caroline Rickard (ABT 1734-)
| | | +---Honour ?
| | +---John Trethewey (ABT 1785-)
| | | +---Charity Strangeman (1756-)
| | +---John Trethewey (ABT 1810-05 NOV 1885)
| | | | +---Richard Whetter
| | | +---Mary Whetter (ABT 1789-JUN 1828)
| | | +---Mary Bullon
| +---Ann Trethewey (ABT 1839-10 AUG 1901)
| | +---John Goodge (-BEF 1851)
| +---Ann Goodge (ABT 1813-05 MAR 1890)
| +---Jane Yelland (ABT 1773-)
+---Stanley (Stan) Trethewey
| +---Edith Broad (1877-)
Carol Trethewey
+---Constance Iredale