Legal Question in Family Law in Arizona

I would advise your son to go ahead and file an action for establishment of paternity (after consulting with a qualified attorney). You don't necessarily have to have information such as where she lives and her date of birth to file a petition. It sounds like you know how to get in touch with her in some fashion, so all hope is not lost. Some options for service of process include sending certified/restricted delivery/return receipt mail to her last known address, process server (if you know, say, where she works). Normally you could try service by publication as a last resort, but certain things like paternity cases require personal jurisdiction. Anyway, it is important to take action as soon as possible to put the court (and mom) on notice that he wants to find out if he's the dad, and then hopefully the pieces will fall in place fairly quickly for him to find out if he is in fact the biological father of the child or not. Best of luck!