Complex sentence: Together with her two children, Princess Catherine had been removed from the royal palace, banned from the funeral, and immediately banished from Russia by the Tsar's eldest son, Alexander III, who swiftly rolled back many of the liberal reforms his father had made.
Split into simpler sentences: Together with her two children, Princess Catherine had been removed from the royal palace, banned from the funeral, and immediately banished from Russia. As the new Tsar, Alexander III then swiftly rolled back many of the liberal reforms his father had made.