Complex sentence: Anastasy Andreyevich Vonsyatsky was born in Warsaw, Poland (then part of the Russian Empire) to a privileged Polish family known for its long devotion to the Russian czars; one of Vonsyatsky's great-grandparents had been handed a titled estate from the Romanovs.
Split into simpler sentences: Anastasy Andreyevich Vonsyatsky was born in Warsaw, Poland (then part of the Russian Empire). His family known for its long devotion to the Russian czars; one of Vonsyatsky's great-grandparents had been handed a titled estate from the Romanovs.