Complex sentence: The area around Braemar and Ballater is known as "Royal Deeside", due to the fact that since the reign of Queen Victoria, the British Royal Family have spent their summers here at Balmoral Castle.
Split into simpler sentences: The area around Braemar and Ballater is known as Royal Deeside. Since the reign of Queen Victoria, the British Royal Family have spent their summers here at Balmoral Castle.