Gordon Millar
| +---James Trethewy (ABT 1517-ABT 1573)
| +---Richard Trethewy (BEF 1550-)
| +---Robert Trethewy (BEF 1575-DEC 1623)
| | | +---William Hawkins
| | +---Joan Hawkins 
(ABT 1530-)
| +---Thomas Trethewy (ABT 1596-ABT 1664)
| | +---Ann Burgess (-ABT 1637)
| +---Robert Trethewy (AFT 1642-ABT 1690)
| | | +---William Jolley
| | +---Isabel Jolley (ABT 1606-)
| +---Charles Trethewy (AFT 1673-DEC 1735)
| | | +---John Scawen
| | | +---Trehane Scawen (ABT 1614-)
| | | | | +---John Trehane
| | | | +---Elizabeth Trehane
| | +---Dorothy Scawen (ABT 1653-)
| | | +---Gregory Arundell (-ABT 1653)
| | +---Dorothy Arundell
| | +---Edith Crane (-ABT 1666)
| +---John Trethewy (ABT 1700-)
| | +---Jane Williams (BEF 1683-)
| +---Samuel Trethewy (ABT 1726-MAR 1791)
| | | +---William Perkin (-1688)
| | | +---John Parkin
| | | | +---Mary ?
| | +---Philadelphia Parkin (ABT 1694-MAY 1783)
| +---Samuel Trethewy (ABT 1772-25 DEC 1828)
| | | +---Richard Hendra
| | +---Blanche Hendra (ABT 1734-JAN 1775)
| | +---Jane Murton
| +---John Trethewy (ABT 1799-18 OCT 1874)
| | | +---William Bryant (ABT 1733-JAN 1796)
| | +---Jane Bryant (ABT 1774-13 SEP 1843)
| | | +---Walter Lawry
| | | +---John Lawrey (ABT 1703-ABT 1799)
| | | | +---Julyen Nanjulian
| | +---Thomazine Lawry (ABT 1738-)
| | | +---John Grose
| | +---Mary Grose (ABT 1707-ABT 1757)
| | +---Mary Bellamy
| +---John Trethewy (19 JUN 1822-28 MAY 1912)
| | +---Mary Hawkey (ABT 1798-15 APR 1862)
+---Edith (Edie) Emblyn Trethewy (22 SEP 1901-1934)
+---Emblyn Cordelia Gilbert (10 JAN 1859-02 FEB 1945)