Complex sentence: Grigory Orlov and his other three brothers found themselves rewarded with titles, money, swords, and other gifts, but Catherine did not marry Grigory, who proved inept at politics and useless when asked for advice.
Split into simpler sentences: Grigory Orlov and his other three brothers found themselves rewarded with titles, money, swords, and other gifts. But Catherine did not marry Grigory, who proved inept at politics and useless when asked for advice.