Which character is Mr. Darcy's cousin and Lady Catherine's nephew?

Colonel Fitzwilliam is Mr. Darcy’s cousin and Lady Catherine de Bourgh’s nephew in Jane Austen’s Pride and Prejudice.

He is the younger son of an unnamed earl and the brother of Lady Catherine’s late husband, making him her nephew. Through the same family connection, he is also cousin to Darcy, Georgiana Darcy, and Anne de Bourgh. His first name, Fitzwilliam, is shared with Darcy’s Christian name.

Colonel Fitzwilliam appears at Rosings Park with Darcy and provides Elizabeth Bennet with important information about Darcy’s character. He explains that Darcy recently separated Bingley from Jane Bennet, unintentionally revealing the source of Elizabeth’s anger before Darcy’s disastrous first proposal.

Readers sometimes confuse him with George Wickham because both men are military officers and both know the Darcy family. Fitzwilliam, however, is a trusted relative and co-guardian of Georgiana Darcy, while Wickham is Darcy’s former acquaintance and antagonist.