In December 1936, Henry's brother Edward VIII abdicated the throne to marry divorcée Wallis Simpson. His brother, Prince Albert, ascended the throne as King George VI. Although third in line to the throne, following his two nieces Princesses Elizabeth and Margaret, he became the first adult in line, meaning he would act as regent if anything were to happen to the King before Princess Elizabeth came of age on 21 April 1944, her 18th birthday. Because of this, Prince Henry could not leave the UK at the same time as the King. Furthermore, he and his younger brother, the Duke of Kent, had to increase their royal engagements considerably to support the new King.