Iris Trethewy 
| +---James Trethewy (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)
| +---Richard Trethewy (ABT 1867-26 JAN 1927)
| | | +---Samuel Liddicoat (ABT 1820-)
| | +---Emily Liddicoat (ABT 1845-)
| | +---Elizabeth ? (ABT 1820-)
+---Lilian Trethewy (1897-1957)
+---Bessie Hancock (ABT 1872-08 SEP 1938)