Complex sentence: The one failing of their marriage was that it remained childless; nature was unkind to them but Ruth remained optimistic, stating that this had been more than compensated for by the part he had played in her life.
Split into simpler sentences: The one failing of their marriage was that it remained childless. Whatever the case, it is clear that nature was unkind to them but Ruth remained optimistic, stating that this had been more than compensated for by the part he had played in her life.