private investigator

Thoughts? I recently had a early resolution meeting with my ex. He stated he got a private investigator to get my current boyfriends address to send papers. (not my address) I know he's lying but I am beyond creeped out. The thought of some random person I don't know following my family and I. That he paid. I can't believe this is legal. My ex's mother and grandmother had access to my boyfriends address. I didn't tell them I lived at my mothers untill after I had gotten the summons. So when his(my son's) grandparents served me for grandparents rights I got served at my correct address by the sheriffs office.