The Great Kirby Fabrication

In the late 1800s, a man decided to not just change his name but his entire genealogical and racial background. The lie started when he told his children their ancestor owned a castle in Ireland and were wealthy chieftains. The fabrication was even more elaborate than that. It grew to tell his neighbors, and he had to make sure his siblings were onboard as well. Why would he do this? What was he trying to hide?