Simplify the following text for a Grade 9 native English-speaking person.
Original: Princess Augusta ( Augusta Frederica ; 31 August 1737 â `` 23 March 1813 ) was a member of the British Royal Family , a granddaughter of George II and sister of George III .
Simplified: Princess Augusta Frederica ( 31 August 1737 â `` 23 March 1813 ) was a member of the British Royal Family , a granddaughter of George II and sister of George III .