Hi was just wondering if anyone can help me? My boyfriends ex girlfriend changed their son's last name to her husbands last name without concsent of my boyfriend is there anything he could do?

He could fight it if he believes they didn't follow procedure. He needs to go to the court house and get a copy of the judgement. If he simply never responded to anything sent or served to him then he missed his chance. Also was the child born during the marriage?