Simplify the following text for a Grade 7 native English-speaking person.
Original: Francis II of France ( French : FranÃ ois II ) ( 19 January 1544 â `` 5 December 1560 ) was aged 15 when he succeeded to the throne of France after the accidental death of his father King Henry II in 1559 .
Simplified: Francis II of France ( January 19 , 1544 â `` December 5 , 1560 ) was a King of France and a member of the House of Valois .