Prince Gustavus was the son of prime minister, Count Oscar Bernadotte and Countess Sophia, née Princess of Nassau. Although not himself born a prince, he had close ties to European royalty through his mother, and through his paternal grand-mother, Josephina of Leuchtenberg. Gustaf Bernadotte was a professional tennis player, calling himself "Mr G". The couple had three sons: Gustavus Adolphus, who inherited the throne and became the first monarch of the house of Bernadotte William Erik