Charles Darwin's mother, Susannah, was Wedgwood's daughter.
Ralph Vaughan Williams's mother, Margaret Vaughan Williams, was the daughter of Josiah Wedgwood III.
Ralph Vaughan Williams was also Charles Darwin's great–nephew. His maternal grandmother (Margaret's mother) was Darwin's sister Caroline. I think this means that Vaughan Williams, as well as being the great–great–grandson of Josiah Wedgwood, was also his great–great–great–nephew.
Charles Darwin married his first cousin, Emma Wedgwood, who was the daughter of Josiah Wedgwood II (the brother of Darwin's mother, Susannah).
Charles Darwin's most famous antecedent on his father's side was his grandfather, the natural philosopher Erasmus Darwin. Another of Erasmus Darwin's grandchildren (one of Charles Darwin's first cousins) was the Victorian polymath Francis Galton, who invented the term eugenics to refer to the now discredited practice of encouraging the 'right' sort of people to breed while discouraging the 'wrong' sort.
Wikipedia has a detailed article about this family, including an extensive family tree.
Ralph Vaughan Williams's father, the Rev. Arthur Vaughan Williams, was the vicar of Down Ampney – a village in Gloucestershire, between Cirencester and Swindon. Ralph Vaughan Williams was born in down Ampney in 1872. He named one of his best–loved tunes after the village of his birth; it's the one to which we sing the words "Come down, O love divine".
© Haydn Thompson 2017