+---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)
+---Scholyer N Trethewy (1864-1938)
| +---Margaret Eleanor Ross
Marguerite Trethewy (1898-)
| +---James Trethewy
| +---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)
+---Ida C Trethewy (24 MAR 1872-OCT 1963)
+---Catherine Lohness (12 SEP 1844-14 JAN 1898)