You always tell me nicely when I cross the line in giving sound advice and opinionated advice...It is safe to say, you is pretty opinionated.
I believe (especially on this forum) you have to walk a mile in someone shoes before giving moral advice. I have a few cousins in my family that found out that their father wasn't their bio-father and didn't need councelling and didn't call their mothers liers. It answered a lot of questions they had when they found out, but none of them held grudges or needed counseling.
To the OP: Your answer is "Yes" you can try. From a new born til 9 years old she thought (and still thinks) he is her father. Probably helps if the bio-father has absolutely no contact with her and never collected a penny from him. I am guessing he doesn't because your daughter is not aware of who her real father is. I am sure things like having her listed on his health insurance, life insurance policy, and anything else that shows that he took on the roll of "Father" would help your case too.
Does she have his last name????????
It is a long shot, but there is a number of cases where the guy is paying child support for a child that is not their, because they assume the roll as "Father" during the marriage and end up paying support when the marriage ended.
BUT!!!!!....You are already going to get Child Support for two children from him. The difference between claming all three and only claiming the two that is the bio-father is a very small amount. It might not be worth the trouble, because there is only so much you can take from a person paycheck. Think about it. Going after the real father would probably be more beneficial to you, especially if he not already paying child support to someone else.
EDIT:
Sorry....I just remembered I am pretty sure California is one of two states that put a stop to having non-bio father paying Child Support, based on marriage. Better research on that.

