Mary and John Wilkes (called John Wilkes and his daughter Polly) by Johann Zoffany (National Portrait Gallery - London, UK)

John Wilkes’ Wikipedia article is here. Mary Wilkes' article in the peerage is here; she never married.

He is a distant relative of the most infamous assassin in the USA’s assassination-plagued history, John Wilkes Booth.

From the-athenaeum.org.