The fourth Francis Willoughby (1668 - 1688), son of the naturalist, died at an early age. He was, however knighted, an honour that was earned but not received by his father who also died young. Francis and his siblings were tutored by John Ray from 1572, when their father died, until the second marriage of their mother (née Emma Barnard) to Sir Josiah Child. The children were unhappy under the revised arrangements and when Francis was about eighteen he set up house at Wollaton with Cassandra as his housekeeper. He had to go to court to have his inheritance restored to him.
Francis died only two years later.