Stepson's mom not married to military boyfriend, can SS be on his military insurance?

[Claire Nicole]

My stepson's birth mom put him on her boyfriend's military insurance plan, along with his six kids. She did this while my husband was in between jobs and therefor insurance plans.

My SS does not live with her, and never has. The custody papers state my husband is responsible for the insurance payments, and that they must split all fees not covered by insurance.

The last time she swapped insurance plans, she refused to send proof and we sent payments to avoid her drama. We found out we were also paying for her OTHER three children belonging to other fathers, and stopped right away.

We refuse to send her payments until we know how much it costs JUST for him, and if he can even legally be on this insurance. From what we've read, only the birth, adopted, and step-children of military members can be on this plan. I've read that if they are not any of those, it is considered fraud and all who use the insurance are guilty.

Does anyone know here if there are legal issues with his insurance? Also, would anyone using such a plan be able to tell me what he costs if it IS legal? We'd hate to go through court and have legal fees over this, but it's looking like that's the way to go if she doesn't start cooperating with us. We have sent many e-mails and texts, and have made many phone calls and never get her to reply. She just sends the occasional, "You and your b***h owe me money" emails and that's about it.

She has started posting rants about on my poor SS's Facebook page and statuses, and I'd just really like to deal with this asap for his sake. Thanks in advance for any help~