+---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 ?
+---Joseph Trethewey (ABT 1793-)
| +---Charity Strangeman (1756-)
+---Benjamin Warrick Trethewey (ABT 1815-1877)
| | +---Benjamin Warrick
| +---Elizabeth Warrick (ABT 1788-)
| +---Jenifer ?
+---Benjamin Trethewey (ABT 1849-)
| | +---James Coombe
| +---Jane Coombe (ABT 1815-)
| +---Jenepher ?
+---Frank Trethewey (ABT 1894-)
| +---Eliza Jane Ward (1862-)
Christopher Trethewey (1927-FEB 1999)
+---Hetty Selleck