(ABT 1858-)
+---Richard Henry Northcott (26 JUN 1884-20 JAN 1927)
| +---Elizabeth Jordon 
(ABT 1855-)
Dorothy May Northcott (03 FEB 1910-)
| +---Nicholas Trevithick (ABT 1618-FEB 1698)
| +---Thomas Trevithick (ABT 1664-MAR 1723)
| | | +---Thomas Couch
| | +---Peternell Couch (ABT 1640-DEC 1696)
| | +---Elizabeth ?
| +---Thomas Trevithick (ABT 1697-FEB 1771)
| | | +---John Peters (ABT 1639-)
| | +---Mary Peters (ABT 1665-)
| | +---Marrian Spry (ABT 1643-)
| +---Thomas Trevithick (ABT 1736-MAR 1804)
| | | +---John Bennett (ABT 1680-JAN 1717)
| | +---Mary Bennett (ABT 1706-1742)
| | +---Pricilla ? (ABT 1680-)
| +---John Trevithick (ABT 1778-DEC 1854)
| | | +---John Sarel (ABT 1707-)
| | +---Rebecca Searle (ABT 1733-MAY 1823)
| | +---Jone Pasco (ABT 1711-)
| +---Thomas Trevithick (ABT 1806-1887)
| | | +---Richard Parrow (ABT 1752-MAY 1824)
| | +---Honor Perrow (21 APR 1782-1857)
| | +---Jane Sara ? (ABT 1749-JAN 1823)
| +---John Trevithick (ABT 1834-07 SEP 1885)
| | | +---Thomas Bassett (ABT 1779-)
| | +---Susanna Bassett (ABT 1805-1891)
| | +---Elizabeth Glanville (ABT 1783-)
| +---William John Trevithick (07 OCT 1857-01 APR 1928)
| | | +---William Kennedy (ABT 1805-)
| | +---Ann Kennedy (ABT 1831-1903)
+---Eliza Wills Trevithick (20 JAN 1885-09 AUG 1952)
| +---George Tonkin
| +---George Tonkin (1758-)
| | +---Jane ?
| +---James Prout Tonkin (ABT 1800-)
| | +---Jennifer (Jane) Prout
| +---William Tonkin (ABT 1831-)
| | +---Jane Tredinnick
+---Elizabeth (Bessie) Paull Tonkin (ABT 1862-1942)
| +---Joseph Wills
+---Eliza Wills (ABT 1828-)
+---Martha ?