Father Wants to Add His Name to Child's Surname After Paternity Determination

My question involves name change laws in the State of: PA
I was just petitioned by babys father to change child name (2yr old) to his last name/hyphenate and I plan to file objection. What do I state? I know its "in the best interest" but examples (wording) of y its not would be helpful
summary is: he denied aop @the hospital, within 2 months, did sign and we sent it. 2 weeks afterwards after a domestic violence issue on his part he hired attorney to rescind the aop in which they did. 5 months later I filed for support and he wanted a paternity test. We did so and of course it came out him being father and a support order was entered. He immediately filed for sole custody. We now share custody and he wants baby's name to be changed to his. Let me remind you, not once nor twice but now for the third time he decides to do this. We were never married and babys lastname since birth is my last name.

He has an excellent chance of getting a hyphenated last name, if not a complete last name change.

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(The AOP is a complete non-issue and won't matter at all)