Complex sentence: Zahorski's great grandfather was-a renowned Polish chess player and activist who was exiled to Moscow, where in 1917 his son, Jerzego, Zahorski's grandfather was born.
Split into simpler sentences: Zahorski's great grandfather was-a renowned Polish chess player and activist who was exiled to Russia. In 1917 Eugeniusz's son, Jerzego, Zahorski's grandfather was born.