+---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
+---John Trethewy (25 DEC 1805-1871)
| +---Catherine Scholier
+---John Neal Trethewy (26 AUG 1840-03 SEP 1878)
| +---Margaret Grinton (24 APR 1810-1860)
William Alexander Trethewy (1870-)
+---Catherine Lohness (12 SEP 1844-14 JAN 1898)