+---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 ?
+---Benjamin Trethewey (ABT 1802-BEF 1861)
| +---Charity Strangeman (1756-)
+---Richard Trethewey (19 NOV 1829-18 APR 1897)
| | +---Richard Thomas (ABT 1763-)
| +---Elizabeth Thomas (ABT 1808-)
| +---Mary ?
+---Jabez John Warne Trethewey (07 SEP 1864-1935)
| | +---John Warne
| +---Naomi Warne (ABT 1834-1912)
| +---Mary ?
+---William Hilliard Trethewey (16 AUG 1898-18 MAR 1981)
| +---Margaret (Maggie) Ellen Wright (07 DEC 1873-19 OCT 1950)
+---John Hilliard Trethewey (03 JAN 1941-08 DEC 2007)
| +---Della May Button (30 NOV 1901-24 OCT 1993)
Colin Edward Trethewey (25 MAY 1969-)
+---Anne Wendy Finch-Noyes (19 OCT 1941-)