I assume you have seen or possess a copy of the Martyn family tree.
The few paragraphs I paste below could help you a little. I would be happy to help further if you are prepared to post your email.
My grandmother, Jean Margaret Martyn, was born into a wealthy family – the Martyns lived in a substantial house on Wimbledon Common, Gladswood, No 9 Southside. Her father, William Edward was a successful lawyer, practicing in the Middle Temple.
The Martyns came from St Columb Minor in Cornwall, a small village just inland from Newquay, where the family can trace its roots back to the 17th century – the first record being that of Thomas Martyn, born in 1668. Thomas was a yeoman farmer, the founding father in a Martyn family tree commissioned in the mid-19th century. (See below).
William Edward’s father, William Martyn, was a physician and surgeon, born in St Columb in 1815, who was himself the son of a local doctor, Dr Thomas Martyn (1774-1826). Thomas’s brother, William (1817-1815), who drowned in the nearby Gannel Estuary, is commemorated in the east window of St Columb’s parish church. The churchyard is stacked with Martyn tombstones.
William Edward evidently prospered and set up home in considerable style in London at 6 Trevor Place in Knightsbridge in a household with three live-in servants and practiced in nearby Trevor Terrace. He later moved to Westmoreland Lodge, Wimbledon, where he died in 1896.