Complex sentence: There he met Gurdjieff and took in Mme Sophie Grigorievna Maximenko as his wife but he had a mistress by the name of Anna Ilinishna Butkovsky.
Split into simpler sentences: There he met Gurdjieff and took in Mme Sophie Grigorievna Maximenko as his wife. He had a mistress by the name of Anna Ilinishna Butkovsky.