Who is Leir and his three daughters: Regan, Goneril and Cordelia from The History of the Kings of Britain and what is their importance?

Leir is the King of Britain for sixty years. He has three daughters, and he decides to test their love in order to fairly divide his kingdom among them. His youngest daughter, Cordelia, gives an unsatisfactory answer. As a result, she is cut out of her father's "will" and married off to a foreign man. Regan and Goneril, his other daughters, profess their love exuberantly and are given equal shares of the kingdom. Once Leir hands over the land to his eldest daughters, however, they turn on him and refuse him a home. They go on to successively strip their father of his wealth and pride until he is a penniless beggar. He manages to secure passage across the sea to the home of Cordelia, and when she sees her father's state, she immediately provides for her father's return to glory. Along with her husband, Cordelia overthrows her sisters and repositions Leir on the throne. When Leir dies, Cordelia takes control.