Who is Randolph Churchill from The Last Lion: Winston Spencer Churchill and what is their importance?

Randolph, the father of Winston, meets Jennie when she is nineteen years old. They are quickly engaged and married when she is pregnant with Winston. After his wedding, he settles into a house in Mayfair, and then he and his wife are summoned to his parents' country home, where they remain until baby Winston is born. He then returns to Mayfair with his wife and child. Randolph's family is good friends with the royal family, until Randolph's falling out with the Prince of Wales.