Can the non custodail parent pay less if the custodial parent remarries?

Probably not, unless there is an additional change in circumstance. Child support is generally based on a formula that takes into account things like income (or income earning potential), health insurance, child care and other expenses. The income of the new spouse is not one of the factors in this calculation. However, support of another minor child is, so if the custodial parent has another child in that marriage, that may affect the calculation.

You'll need to check the laws in your state but in most states the spouse's income is not factored in unless the custodial/non custodial parent is living solely off of his/her spouse's income.