Legally, the answer is supposed to be no.

Your fiance's child support is between him and his ex-wife. The court is supposed to only consider their paychecks each month, and not your's or her new significant other.

Unfortunately, a judge can do what s/he wants within the law. I have seen judges who DO take the new spouse's income into consideration when re-figuring child support. (I was present at one case where the judge did this. The new wife objected (through the lawyer) and the judge responded, "When the ex-wife gets re-married, I will take her new husband's pay into account to re-figure child support.")

Daddyevil

Your income should in no way reflect your soon to be spouses child support obligations. Of course there are exceptions to every rule, however, I'm certain you'll find that the vast majority of cases will not include a new spouses income when calculating support.

The chance of your income becoming a factor are very slim.

There are other factors that control how and when a parent can request modification of child support as well that may prevent his ex from filing. There are certain requirements most states have the prevent a parent from filing for modification, such as length of time since the last modification. It varies by state but it may be worth knowing for piece of mind.

Good luck to you and congatulations on your upcoming wedding.