Who pays medical bill of dependant?

[Schwippsy]

What is the name of your state (only U.S. law)? IL
My two sons were on fathers health insurance their first two years. I took my one son to an annual check up while he was on the father's insurance. Insurance paid some, but not all vaccinations, so there is a $400 open bill now. The father has now taken off and become a deadbeat and is not paying this outstanding bill. After his disappearance and since the kids were on my health plan, I have always paid open bills for my kids on my insurance right away.
Now that they do not get my ex to pay the bill, they are coming after me. We have not been married. I have no access to his previous health insurance to confirm the charge of this pediatrician are correct. In my eyes this is the father's bill to pay, not mine.... am I right? What is the legal point on this?
Many thanks for your help.

 

[Zigner]

Did you sign the paperwork at the doc's office?

You agreed to be responsible for any amounts the insurance didn't pay.

 

[ecmst12]

As far as the doctors office is concerned, both parents are jointly and severally liable for the bills of minor children. That means they can pursue either or both of you. Since dad didn't pay, they are within their rights to bill you, and you should pay it. You can always go after dad yourself for his share later (if you can find him) and this will protect your credit rating.