Legal Question in Family Law in Minnesota

You do not have a child support obligation for your wife's child from a previous relationship, unless you adopted the child during your marriage. In that case, the child is "yours" as a matter of law, and you would have to pay child support. If you did not adopt her child, then you have no obligation for support.

You also asked whether you could avoid a child support obligation if she agreed to waive her right to child support in an antenuptial agreement (also called a prenuptial agreement). (This assumes you have a child support obligation in the first place.) The simple answer is that child support cannot be waived under any circumstances, whether in an antenuptial agreement made before a marriage, or in an agreement made after the marriage. Such agreements are unenforceable as a matter of law.