[3] Details of Richard's life and family background are scarce, with many legends and rumours, and as a result tracing ancestry beyond him has proven difficult.

On the subject Lord Moyne, writing in The Times in 1959, wrote: The origins of our family are hidden in the mists of a not very remote antiquity.

[3] A romantic and fanciful rumour existed that Richard Guinness was the illegitimate son of Viscount Magennis before he fled to the Continent.

Instead, based on DNA testing conducted by Trinity College Dublin, Patrick Guinness asserts descent from the Macartans, a lesser County Down clan under the Magennises.

Parallel and contrasting the Magennis theory, one rumour was that Richard Guinness was the illegitimate son of an English (i.e. Williamite) soldier stranded in Ireland after the Boyne, and an Irish girl.

[5] Henry Seymour Guinness, of the banking line, who was also the first to suggest "Owen Guinnis" as the father of Richard, was the main proponent of Cornish origins.