If you are not legally married to your partner, then you will have to purchase 2 separate policies. Even if you are legally married, it is still best to purchase 2 separate policies. Since travel medical insurance pricing is regulated by the Department of Insurance, the pricing and benefits are the same whether you purchase 1 combined policy or 2 separate policices. The benefit to purchasing 2 separate policies is that you are able to make changes to the polciies independently from one another. If you had purchased 1 combined policy, any changes you want to make to one insured would have to happen to both insureds; this is why we always recommend purchasing separate policies.
Insurance rates are regulated by law. You can't find the same insurance plan for a lower price anywhere else