Yes, I can place them on the Martyn tree; I've pasted him and his children below. He was son of John M (1737-99), son of Joseph, son of Thomas ..
How do you connect to the C19 Martyns?
Denis
4 William MARTYN b: 1775 c: 27 DEC 1775, of Trevithick?
- drowned in the Gannel (estuary, Crantock/Newquay) 15 Oct 1815 acc. Bibliotheca Cornubiensis
- m Elizabeth Darke 11 Nov 1802, Hatherleigh
5 John Darke MARTYN b: 1804 - d 1877
- b Trevithick, 30 Nov 1803, d Padstow 27 Jan 1877; m 29 Jan 1834 Bodmin SSH of Treharrock, St Kew
+ Susan Symons HAMBLY b: 1805 c: 20 JAN 1805 d: BEF 1871
5 Elizabeth MARTYN
5 Caroline MARTYN - b 1807/8, d ca Feb 1899, St Columb
- paid for "Martyn window" at St C Min
5 Mary MARTYN - b 1808/9, m ca Aug 1852
+ Constantine Bradford JOHNS b: 1805 -(also m(1) Mary Martyn, ca May 1838)
5 William MARTYN b: 1811 - merchant & farmer at Trevemper Bridge, 1851
- leased Polwhele, Trevemper Bridge, from his brother in 1836
5 Gertrude MARTYN
5 Thomas MARTYN b: 1813 (1812?)-1893 (Bodmin ca Nov)
+ Susanna Symons MARTYN b: 1812