New Hampshire Might Legalize Civil Unions For Everyone—Including Siblings:
"Asked about the logic behind allowing siblings to enter into civil unions, Bates responded, “You have that question backwards. By definition in the bill, a ‘civil union’ means a contractual agreement that provides reciprocal benefits and obligations to the parties to the agreement.”
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http://www.businessinsider.com/new-hampshire-might-legalize-civil-unions-for-everyone--including-siblings-2011-10