Gossip and a fallacy

I have heard it said that my older sister is under no obligation to help our elderly parents---- because her husband did not help his own parents......Well, perhaps it was never said. Perhaps I have misunderstood, .....but it is worth pointing out what a stupid and barbarous thing that is to say! He should have helped his parents! And if he did not: Shame on him! He has nothing to be proud of. To repeat an error on grounds of consistency is not clever or just; it is idiocy. It is no virtue to be consistent if the first thing you did was wrong.