Simplify the following text for a Grade 5 native English-speaking person.
Original: Mary 's uncle was King Charles II , who ruled the three kingdoms of England , Scotland and Ireland ; her maternal grandfather , Edward Hyde , 1st Earl of Clarendon , served for a lengthy period as Charles 's chief advisor .
Simplified: Mary 's uncle was Charles II . Her grandfather by her mother 's side was Edward Hyde , 1st Earl of Clarendon .