Child support question paying parent?

well my husband has 2 kids to a previous relationship, he has a family and a wife of his own to support as well they want 1000 a month out of him. Dosent matter what she earns or what her husband earns we still have to pay, we are finiacially trying to live ourselves and they don't care... it is going through the procedure through ird at the moment, but if its nothing outstanding out of the ordinary they just say pay, they turned around and said if we took it to caught they would say sell the house, so all the saying is the other two children come first before our ones in our own home,,, i think that is disgusting these kids are no different to the others and the oldest of the other one is working 25 hours as well.. we want a change and want to know why, our kids should be just as important as well, we are not entitled to government subsidy as well, we earn to much but because we have to work is to pay for everything and we still cant afford to, because we get penalised the more we earn the more child support goes up so we are getting no where... so dosent our children have a right as well to have a life as well or you going to take there house away from them so the other two can get money to live a bit happier, when they have two incomes coming in and they own there own farm, you dont look at there finiacials but ours comes straight into it.. please help me understand because i dont understand it at all.. i thought all the kids have a right in the country...