The father's father has no legal duty.
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Neither of the fathers has a legal duty to provide support. Since the accident happened on a road, I assume this was an accident involving a vehicle. Since the injury is so serious, make sure that you contact a lawyer immediately! DO NOT WAIT. Make sure that your lawyer finds out if there was a defective condition with the road, sign, traffic light or something else. In NY, you have 90 days from the accident date to file a Notice of Claim against a government entity.
My answer is for general information purposes (a little more than entertainment) and I do not give legal advice without a personal consultation in New York. I am only licensed to practice law in the State of New York and my answer here pertains to a general question in NY.
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