I live in Florida. My friend and his wife adopted his son and his sons sister, who is not related to my friend. Their mother wanted them back, so my friend signed over guardianship to her. Now she doesn't want them again, and is telling my friend he must take them back because they are the adoptive parents. What, if anything, can they do to revoke their rights? The kids are about 13 and 16.

"signed over guardianship" was this thought the court ? And I guess I have to ask why since they went to all the trouble to adopt.

But yes, if they are the adoptive parents they are responsible.

My issue is about the kids, what is going to happen to them since no one wants them. They need a home, and love and at this point counseling

If this was a legal adoption then the mom had NO rights to the kids and your friend just can't sign over guardianship. Sounds like a lot of illegal actions with using a court.

Thank you, yes it was a legal adoption. The mom told the court before they were adopted that she didn't want them, and they were going to put them in foster care. So to prevent this, my friends took them both. The bio mother kept in communication with them, and was constantly saying things to them about my friends. She is now threating my friend, his wife and his wife's daughter. Because of the bio mothers influence on them, they "hate" my friends who have done everything for them. As for the guardianship, when the mother said she wanted them, they went to their cousellor who helped them before and told them what to do. I could be just a temporary thing, I'm not sure.

Unless the adoption was specifically an Open Adoption then your friends screwed up by letting the bio mother continue contact.

Now this has become a legal mess and they need an Family Law attorney to unravel it.