Is it a violation of HIPAA laws for a healthcare worker to "friend" a patient's family member on Facebook or other social media sites?

If they became acquainted through the patient, then yes. And it would be a violation to discuss the patient in any medical way.

I agree it would be a violation to share health information but how they became acquainted is not material to HIPAA. I am new to Facebook but it seems the way you friend someone is to notice they are a friend of one of your existing friends so you send them a request, right?