I am unsure of your exact question (is it 'can the name be hyphenated or how can you stop such a request). There is a great deal of information needed to address you primary concern, which seems to be control. Has the father been adjudicated? Or has a paternity action even been initiated? If not, you have sole custody of a child born to yourself out of wedlock, though if a paternity action has been commenced (or may be commenced), the issue of the child's name is one the father can have input on (assuming joint legal custody) and even request relief on in the paternity action (when they re issue a birth certificate with his name), as well as primary placement and legal custody. I strongly suggest you seek the assistance of a Wisconsin licensed attorney that specializes in paternity cases, not just family law, as you are dealing with a very specific area of family law many general attorneys do not know very well. Good luck.
This answer is for informational purposes only. By answering this question, no attorney/client relationship is created between the question poster and JCWB ESQ LLC. Although the legal information is accurate, with the facts presented, it may not be appropriate and/or the best solution for your entire situation. The best way to handle any legal problem is to seek the advice of an attorney licensed in the jurisdiction where the issue arises.
Wisconsin law says that at the time of a paternity adjudication, the court may hyphenate the child's last name if requested by one of the parties and finds it is in the best interests of the child to do so. However, if the paternity judgment has already been entered, there is no provision in the law for the court to then later change the child's name. He would have to file an actual petition to change the child's name for which you are entitled to notice and the right to object.
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