Complex sentence: The sisters lived alone with the servants until October when Grand Duke Boris' dacha was expropriated and they were evicted and forced to move to Petrograd with their mother and their half-sister Marianne.
Split into simpler sentences: The sisters lived alone with the servants until October when Grand Duke Boris' dacha was expropriated and the sisters were evicted. Natalia and Irina were forced to move to Petrograd with their mother and their half-sister Marianne.