If you choose to marry someone who is disabled and has a child, your child support will not be lowered. You do not have any legal obligation to support someone else's child (even if a step child), and your choice to support someone who is disabled cannot be used to deprive your own child of proper support. I am unclear if you have a question about the name change. You were supposed to have received notice of that proceeding, and if you did't (check the court file to find out) you may be able to object now. Your ex will not be able to take your rights if you are properly exercising joint legal custody (assuming you have it) and all of your visitation so as to maintain a bond with your child.
Responses are for general information purposes only, and are based on the extremely limited facts given. A consultation with an attorney experienced in the area of law(s) indicated in the question is highly recommended. Information and advice given here should not be relied upon for any final action or decision, as the information is limited by its nature to the question asked and the fact(s) presented in that question. THIS RESPONSE DOES NOT CREATE AN ATTORNEY/CLIENT RELATIONSHIP, particularly considering that the names of the parties are unknown.
I agree with Ms. Whitbeck. Though statute allows for a reduction of child support when a parent has an obligation for another child, your child support will not be reduced merely because you've married someone with a child (disabled or not). That might change if you've adopted that child, but the presence of that adopted child is not the only factor the court will consider. As to the name change, you should have been notified, though these are often done through publication in a major newspaper. There are several requirements for name changes that, if your ex failed to follow, may allow you to "undo" the change. You should see Ms. Whitbeck so that she can advise you after she understands the entire picture.
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