You husband has a responsibility towards his family. If they are taking some money from their son that does not make them greedy. However , it’s your husband’s job to maintain a balance and fulfil needs of his parents and you n children equally. If he is making you and his children suffer financially that is his fault he needs to communicate that to his parents and request them to allow him to adjust the money in a way that he may also be able to fulfil his responsibilities towards you and his children. In my opinion as long as he is not asking you to earn for his parents he is not wrong and can send the money earned by him to his parents as long as he wants.
and husband chahay only son ho ya uskay 10 bhai aur hon this does not reduce the responsibility he has towards his family.