+---Richard Trethewy (ABT 1665-JAN 1741)
+---William Trethewy (ABT 1694-)
| +---Ann Martyn 
(ABT 1666-JUN 1738)
+---James Trethewy (ABT 1719-)
| +---Jenefer Sweet (-SEP 1733)
+---William Trethewy (ABT 1753-)
| +---Grace Warne
+---Richard Trethewy (02 FEB 1799-24 DEC 1875)
| +---Catherine Scholier
+---John Trethewy (25 JUL 1823-24 SEP 1876)
| +---Catherine Hooper (25 MAR 1796-06 DEC 1893)
+---Austin Trethewy (-03 JAN 1924)
| +---Margaret Eleanor Ross
+---Lamont L Trethewy (06 JUL 1885-20 DEC 1948)
| +---Catherine Lohness (12 SEP 1844-14 JAN 1898)
+---Clifton Trethewy (13 OCT 1912-)
| +---Emogene M Bannister (20 APR 1889-11 JUN 1977)
Dorothy Ann Trethewy (05 OCT 1939-)
+---Dorothy Giblin