Whether or not you realize it, having two health insurance plans is common. For example, spouses can have their own policy while also being covered by each other’s employer plan. Young adults (those under 26) can have health insurance from their employer and coverage from their parent’s policy. In the same way, if you’re under 26 and married, your spouse’s and parent’s policies can cover your medical expenses. A child can be covered by both parents’ health insurance (assuming they have individual plans).
However, your insurers won’t receive your bill simultaneously, so they can’t cover the same medical expense. These are subject to primary and secondary insurance rules, so one will be billed before the other. You can’t earn from a medical need because although your second policy may help you with the costs from your first, your total coverage can’t be more than 100% of your health expenses.