Here is the situation... My husband has raised his daughter for the last 13 years of her life (since birth), knowing there is a chance that he is not the biological father. In fact another mans name is on the child's birth certificate. My husband has legal custody of the child and she has lived with him for most of her life, visiting her mother on some weekends.

Just recently the child has found out that the man who has raised her may not be her actual father and has come in contact with the man who is named on her birth certificate. This other man has claimed that he wants a paternity test done after 13 years of the child's life. The child also wants to get it done as she is curious of the results. The mother does not want to have it done, but the child is starting to act out over the issue.

If the paternity test were completed and it was found out that this other man is the biological father, what rights would the non biological father have? Does a 13 year old have a say in court decisions?

This is a legal issue, not a parenting issue and has been moved here.

You state that your husband has "legal custody". How did that come about?

As to whether the courts will allow a paternity test or not, depends on where you live. A key fact you left out. Laws vary by location. In some cases your husband would be deemed the legal father no matter what the paternity test shows. In others, the bio father could have his legal rights affirmed.

As to the 13 yr old, it again depends on the locale as to how much weight is placed on her preference. But only the court will make this decision.

I would strongly suggest that you consult a Family Law attorney immediately.

We live in California. My husband was deemed the custodial parent of the child in question and another child in his divorce. He shares split custody with the mother however he is the main custodial parent.

I would suggest reading the divorce settlement. Its important to determine whether he was ever designated the legal father. Since someone else is on the birth certificate, at some point he should have been.