I only recently learned that my ex-husband and one of his subsequent wives got my daughter adopted by his wife and I was neither contacted nor told of this and certainly never would have approved it. It appears that they lied and said that I had abandoned her which is totally untrue. He eventually got custody (long story) but I was, of course, granted visitation. However, every time my new husband and I tried to do any visitation, my ex either was not home or had a doctor's excuse to prevent us from doing so. I also learned that he lied to her telling her I was dead and intercepted all cards, gifts, etc. to her. I am not sure how old she was when this "adoption" took place, but we were reunited when she turned 16 years old. Apparently a new birth certificate was issued and lists my ex-husband's wife as the mother. What is the statute of limitations on this for me filing a lawsuit against them?

We have an important principle in this country (assuming you are in the U.S.). It's called "federalism". One thing that it means is that the states, for the most part, set the laws on such things as adoptions, including statutes of limitations for suits such as that you have in mind.

In other words, we cannot answer you without knowing what state you are in. :)