(ABT 1517-ABT 1573)
+---Thomas Trethewy (-ABT 1616)
+---Bartholomew Trethewy
+---Bartholomew Trethewy (-1666)
+---Bartholomew Trethewy
+---Thomas Trethewy (ABT 1675-MAY 1743)
| +---Jane Bruart 
+---William Trethewy (ABT 1712-JAN 1777)
| | +---Phillip Mellow (ABT 1660-JAN 1711)
| +---Joan Mellow (ABT 1680-)
| +---Jane ?
+---Richard Trethewy (ABT 1753-MAR 1836)
| +---Grace Rickard
+---Thomas Trethewy (ABT 1797-)
| | +---John Cundy
| | +---Solomon Cundy (ABT 1690-DEC 1759)
| | +---William Cundy (ABT 1733-)
| | | | +---David Pearce
| | | | +---Isaack Pearce (ABT 1666-)
| | | | | +---Alice ?
| | | +---Alice Pearce (ABT 1698-NOV 1739)
| | | +---Alice ?
| +---Susanna Cundy (ABT 1761-)
| +---Jane Treneman (ABT 1737-ABT 1809)
+---James Trethewy (ABT 1845-BEF 1881)
| +---Mary Maneer (ABT 1803-BEF 1871)
+---James Trethewy (27 JAN 1873-05 JUL 1928)
| | +---Samuel Liddicoat (ABT 1820-)
| +---Emily Liddicoat (ABT 1845-)
| +---Elizabeth ? (ABT 1820-)
+---Stanley James Trethewy (04 JAN 1916-26 MAR 1952)
| +---Beatrice Mary Williams (1886-)
Mary Catherine Trethewy (20 MAY 1939-09 MAY 1993)
+---Mildred Virginia Watson (12 DEC 1919-17 OCT 1981)