(ABT 1517-ABT 1573)
+---Thomas Trethewy (-ABT 1616)
+---Bartholomew Trethewy
+---Bartholomew Trethewy (-1666)
+---Bartholomew Trethewy
+---Thomas Trethewy (ABT 1675-MAY 1743)
| +---Jane Bruart 
+---Thomas Trethewy (ABT 1710-FEB 1795)
| | +---Phillip Mellow (ABT 1660-JAN 1711)
| +---Joan Mellow (ABT 1680-)
| +---Jane ?
+---Thomas Trethewy (ABT 1735-SEP 1814)
| | +---Richard Jolliffe
| | +---Robert Jolliffe
| | +---Robert Jolliffe (ABT 1546-1602)
| | +---Henry Jolliffe (ABT 1586-)
| | | +---Thomason ?
| | +---Francis Jolliffe (ABT 1622-)
| | | +---Blanch Pearce
| | +---James Jolley (ABT 1682-APR 1754)
| | | +---Rose May
| +---Elizabeth Jolley (ABT 1713-)
| | +---Richard Osborne (-JUN 1667)
| | | +---Eme Varcoe
| | +---Richard Osborne
| | | +---Joan ?
| | +---Richard Osborne (-NOV 1707)
| | | | +---Arthur Michell (-ABT 1657)
| | | +---Constance Michell (ABT 1635-APR 1717)
| | | | +---Thomas Corne (-1647)
| | | +---Blanche Corne
| +---Blanche Osborne
| +---Bettres ?
+---William Trethewy (ABT 1771-ABT 1827)
| +---Wilmot Hicks (ABT 1731-MAR 1816)
+---Richard Trethewy (ABT 1822-01 NOV 1892)
| | +---John Kellow (ABT 1748-)
| +---Catherine Kellow (ABT 1781-)
| | +---John Pomeroy (ABT 1692-)
| | +---Richard Pomeroy (ABT 1718-)
| | | | +---Hennery Stoneman (ABT 1656-)
| | | +---Thomasin Stoneman (ABT 1693-)
| | | +---Thamasin ?
| +---Catherine Pomeroy (ABT 1747-)
| | +---Robert Philp
| | +---James Philp (ABT 1688-MAR 1764)
| | | +---Anne ?
| +---Mary Philp (ABT 1716-)
| +---Catherine ?
+---Richard Trethewy (ABT 1855-02 FEB 1928)
| | +---Abel Williams
| | +---James Williams (ABT 1797-)
| | | +---Elizabeth Bishop
| +---Jane T Williams (ABT 1828-)
| | +---Martyn Glanvill
| +---Mary Glanvill (ABT 1793-)
| +---Mary Hockin
+---Henry Trethewy (1885-)
| | +---Richard Burley (ABT 1825-)
| +---Martha Burley (ABT 1857-)
| +---Martha Nettle (ABT 1826-)
+---Bradford Trethewy (17 FEB 1921-)
| +---Elsie May
Bradford John Trethewy (1949-)
+---Florence G Ward (-1964)