(-JUL 1733)
+---Richard Trethewy (ABT 1720-)
| +---Isabel Beaubery 
(-FEB 1732)
+---Philip Trethewy (ABT 1765-)
| +---Ann Jewell
+---Robert Varcoe Trethewy (ABT 1804-)
| | +---Robert Varcoe
| +---Grace Varcoe (ABT 1774-)
| +---Joan Benny
+---Richard Trethewy (ABT 1833-30 MAY 1893)
| +---Ann Guard
+---William Trethewy (21 FEB 1864-24 MAY 1949)
| +---Priscilla Parsons (22 DEC 1844-14 NOV 1911)
+---William Arthur Trethewy (24 OCT 1897-14 AUG 1988)
| +---Katherine (Kate) Phillips
William Arthur Courtney Trethewy (13 SEP 1926-)
+---Mona Guinevere Courtney (02 JAN 1898-2005)