50/50 custody and child support

[create71]

My second husband has two children from his first marriage and I also have two children from my previous marriages (totaling 4).  We both have 50/50 custody of the kids.  My ex makes well over 70% of what I make, but I receive no child support (never sought it, thought it was fair to not do so since 50/50 custody...trying to be responsible and 'nice').  My second husband makes about 40% more than his ex, but he pays almost $900 a month in child support, and provides insurance and splits all costs on top of it.  He was not ordered by a judge to pay this, but agreed for fear of her trying to take the kids from him.  Can we lower the amount he pays for child support now that she is making considerably more money than she was at the time?  We are both on the short end of the stick with our respective situations- even though the income disparity is greater with me and my ex, the is no child support, yet my husband pays a large sum to his ex where there is less financial disparity....both 50/50 custody and joint managing conservators.  Both our ex's are very money hungry and make life difficult for us...where does the law lie and how can we proceed to help our situation become more equitable?  Any advice is VERY appreciated!!

[lilywhite]

In Texas, one parent pays child support to the other.  It is based solely on the payor's income and is a straight percentage  25% for two chilren.  The income of the parent receiving child support is of absolutely no consequence to the amount of child support paid.

http://tlo2.tlc.state.tx.us/statutes/docs/FA/content/htm/fa.005.00.000154.00.htm