I have a 5yr old son. I found out he wasn't mine when he was 2. I still am an active part of the child's life. Now his mom wants to throw me on child support. I am on the birth certificate because I thought I was the biological father. What are my options. I do live in Florida.

If you acknowledged paternity when the child was born, then you may be considered the legal father and liable for child support.

Where was the child born and where does he reside now. Has anyone else been declared the legal father?

In Florida, if you are listed on the birth certificate and you were not married, it is because you signed a paternity acknowledgment. Your name can be removed by a court if you can prove that there was fraud, duress, or a material mistake of fact (ie: she told you that you that you were the only possible father)

However, if you have continued to behave as the father in the three subsequent years, and the biological father has not been proved through court ordered testing, you may be out of luck. You set a precedent by continuing to be involved once you knew the child was not yours, and not taking any action to amend the birth certificate as soon as you found out. The court will probably be reluctant to remove you if there is no other father to put into your place on the BC. It is in the best interest of the child to have the support of two parents.

What you have done is amazing and I commend you for sticking around. But, you may be stuck unless the bio dad is found. Even then, it may not help. I'm sorry that being a nice guy put you in a bad situation.