sentences:  In addition, Edward VIII was unmarried during his tenure as monarch, though he then married Wallis Simpson after his abdication (which was caused by this marriage plan).The youngest monarch to marry was David II, who married Joan, daughter of Edward II when he was 4 years 134 days old in 1328.The youngest female monarch at the time of her marriage was Mary II, who was old when she married William III in 1677.