If a man finds out after 15 yrs that he as a child, and she is trying for child support. 1. Is he responsible if he didn't know, and does she get all 15 yrs worth?

And 2. If another man has been in the child's entire life, and it was only determined after medical treatment that he WASN:T the father, is the blood father responsible for back child support? What if the non-blood father is on the birth certificate

Where - it varies by State and Country.