My father passed away, and his 2nd wife had an affair, made my dad sign the certificate, he couldn't have kids and she refused to adopt like he asked. There is an inheritance now in question from my grandparents. The 2nd wife is trying to claim all of it for her daughter. What are the odds that she gets any inheritance when she is not blood, but did live with my dad for awhile.

My father passed away, and his 2nd wife had an affair, made my dad sign the certificate, he couldn't have kids and she refused to adopt like he asked. There is an inheritance now in question from my grandparents. The 2nd wife is trying to claim all of it for her daughter. What are the odds that she gets any inheritance when she is not blood, but did live with my dad for awhile.

I assume she was married to your father when her daughter was born.If he was her presumed father he could not adopt her.
Thus she is legally considered as his daughter and legal heir,notwithstanding her mother's adulterous affairs. As a legitimate child she has all rights.

Inheritance is simply defined as the legal succession of property, titles, debts, obligations and other valuable possessions upon the death of an individual.
Generally in situations where the deceased person has not written any will, surviving spouse inherits the entire property in the absence of children. If the person has any children, spouse receives half / or third/of the property, while the other part is distributed among the children. It depends on your state's law.