Yes, your ex-spouse can object to any deviation that you request. You both have the right to advance any position that you wish to take (request what you want, consent to what you want, deny what you want). A judge will decide whether to grant or deny a requested deviation based on what is being asked for, why it is being asked, and what the objection to the request is. (In other words, and objection does not automatically mean that the request will be denied.)
I hope this answers your question.
~ Kem Eyo
The above answer is a general explanation of legal rights and procedures. It does not constitute legal advice. Nor does it establish an attorney-client relationship between the individual posting the question and the attorney providing the answer.
You will need to legitimate the new child once it is born, once that is done, the court can consider the new child in a child support modification action. Another option is to get married to the mother of the new child. If you are married to the mother you will not need to do a formal legitimization. The child will be considered legitimate if you are married to the mother and therefore the court can consider the child an any future child support modifications.