His eldest son, William. Prince Harry his 2nd son is 3rd in line to the throne.
If Prince William and Kate Middleton do not have any children, then his brother Prince Harry will become King.
Prince Phillip is not in the line of succession, so his death does not affect it in any way.
The monarch in the UK is currently Queen Elizabeth II. The heir apparent is Prince Charles who will become King Charles III when (or if) he succeeds Elizabeth. Prince William will become King William V when (or if) he succeeds Charles.
If he is still alive at the time of her death, then this will be Prince Charles, and if he is not alive it will be his eldest son Prince William.
If prince William does not accept then either his son will be king or there will not be any king
The next person in line to the British Crown is Prince Charles' eldest son, Prince William, and William would the inherit the throne from Queen Elizabeth II.
Rule by a group or family rulers
William's godfather is King Constantine II of Greece.
It is likely that Prince William will become King after his father, Prince Charles.
Constitutionally Prince Charles is currently next in line to the British throne. Whether he succeeds the Queen is his choice.
If Prince William is alive after the death of his Grandmother Queen Elizabeth II and his Father Prince Charles he will become King.
Prince George (born July 22, 2013) is third in line. As of 2016, the line is through Prince Charles (oldest son) to Prince William (oldest son) to Prince William's children (George and Charlotte). They would be followed by Prince Harry (William's younger brother), then Prince Andrew, Duke of York (younger brother of Charles) and Andrew's daughters Princess Beatrice and Princess Eugenie.
Prince William does not give his email or email ID out to the general public. Prince William is the future King of England.
The reason why Prince William isn't in Afghanistan is because he is next in line to be king after Charles becomes king.