If you believe that the medical expenses are covered under these policies, then you need to sue the insurers whom you believe should pay for "breach of contract," or violating their contractual obligation(s) (since insurance policies are contracts) to pay, and also for violation of the "implied covenant of good faith and fair dealing," or the legal obligation that a party to a contract not deliberately act in such way as to deny the other party the benefit of the contract. You don't worry about order of coverage: you name in your lawsuit all insurers whom you believe would have to pay (if coverage order were not a factor) and let them fight it out about who pays first, etc. You sue them for all costs they should have covered but have not.