Is this a HIPPA violation?

My little brother was hospitalized on the 12th of May for asthma related issues and was admitted for the whole week following being seen in our local hospitals ED. I was there with my mother and my brother as support for the both of them. When the woman who supposed to do our registration came in the room all she asked was his name, nothing else. Of course with us being siblings we have the same last name but he is 11 and Im almost 20 which means my records should be seperate and no longer attached to his through our parents. Fast forward to 2 weeks later and I recieve a bill in the mail for almost $6,000 from the hospital since the woman from registration listed me as he guardian instead of my mother. It didnt bother as much since it was family but what if it was some complete stranger who had no relation to me... Would have they been able to recieve any of my health info? I found this to be a little unsettling and Im 4 months pregnant and plan to deliver my child at this same hosptial, but now Im worried how much of my info will be shared if I do. Any advice or opinions would be helpful and appreciated. Thanks.