+---Richard Trethewy (ABT 1665-JAN 1741)
+---Richard Trethewy (ABT 1700-ABT 1764)
| +---Ann Martyn 
(ABT 1666-JUN 1738)
+---Benjamin Trethewey (ABT 1738-)
| | +---Humphrey Harris
| | +---Gilbert Harris (ABT 1637-)
| | +---Gilbert Harris (ABT 1665-)
| | | | +---Richard Wills
| | | +---Jenifer Wills (ABT 1632-)
| | | +---Christian Best
| +---Jenifer Harris (ABT 1696-1780)
| | +---Thomas Hockin (-ABT 1607)
| | +---John Hockin
| | | +---Elizabeth ?
| | +---John Hockin
| | +---John Hockin (ABT 1616-DEC 1696)
| +---Elizabeth Hockin (ABT 1658-)
| +---Blanche ? (-ABT 1699)
+---William Trethewey (ABT 1780-)
| +---Elizabeth Woolcock
+---Thomas Trethewy (ABT 1811-21 SEP 1871)
| +---Sarah Mitchell (ABT 1786-)
+---Samuel Trethewy (ABT 1832-BEF 1881)
| +---Philippa Pearce (ABT 1811-13 FEB 1862)
+---Thomas Trethewey (ABT 1868-1967)
| +---Jane Binney (ABT 1835-)
+---Marshall Grant Trethewey (06 JUN 1900-11 NOV 1961)
| +---Martha Ann Bartlett (26 AUG 1877-08 NOV 1984)
+---Marshall Arthur Trethewey (21 NOV 1936-)
| +---Ada Joynes (09 AUG 1891-24 MAY 1995)
+---Peter Marshall Trethewey (29 MAR 1956-)
| +---Gladys Dawn Crane (31 MAY 1938-)
Janelle Kaye Trethewey (20 NOV 1985-)
+---Kaye Margaret Wilson