How can a person whoms income has changed due to a cutback cut back his child support in order to survive?

my brother lost a good chunk of his income and has children in three different states, he lives in texas now and they live in ct, ma, and ct. he makes his payments but since his income has decrease how can he go to court to get his support payments lowered, all these childrens mothers are unemployed and try to get the maximum amount paid to them and so far has gotten away with it. What are his option he is one of the rare fathers who seriously try to pay support while the women are all out spending. I recommended he takes them to court and have them pay as well towards the childrens survival if not try to get custody of them since he is the only provider. I would like to give him some good advice if there are any attorneys out there with some rea info please get back to me this is a serious matter. Thank you