Catherine Tylney Long was Jane Austen's 4th cousin. Her paternal grandmother, Emma Tylney inherited Tylney Hall through her great uncle Frederick Tylney who died childless. Emma Tylney's Dad was Viscount Castlemaine and her grandmother was Emma Bernard, sister to Jane Austen's GG grandmother, Elizabeth Bernard. (Emma Bernard was married twice. Her other husband was a Willoughby.)

Catherine Tylney Long inherited Wanstead House and a rather nice fortune (she was apparently the richest commoner in England by the time she was 18) when she was just five years old in about 1794. Jane Austen would have been about 19 years old in 1794. Would this have been about the time that JA wrote NA?

Catherine's fortune had a sad end which JA did not live to witness and she (Catherine Tylney) apparently died of a broken heart. Loads more about this family on the Internet - one link below.

Anyone who still thinks the Willoughby and Tylney names are a coincidence should note that Catherine was also maternally related to the Dashwoods. I think this may be the first time that JA used family surnames (she had certainly used family names before e.g. "the Beautiful Cassandra")