Doctor billed insurance we haven’t had in 17 years

We recently began IVF, and provided all of the doctors with our current insurance. I received a bill from our current provider, where as my husband received a bill from an insurance provider he hasn't had since college, more than 17 years ago.
I should note, I have my insurance through my husbands employer. We are not sure how this error happened, but what is more frustrating, is the bill in question, went to my husbands childhood home, where his parents live. My husband and his father have similar names, so my FIL opened the bill in question, not realizing it was for my husband. My inlaws were unaware of our IVF journey, and honestly, we weren't ready to tell anyone.
This has all been frustrating, and I guess my question is, what do we do? Had my in-laws not still lived in their house, we never would have known about this bill. I am not sure if this is a HIPAA issue, or a provider issue.

(We live in NY, my in-laws live in NJ)

submitted by /u/adultorphan2020
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