What makes you think that parental rights can be signed away? You seem to be laboring on some misconceptions about the law and practical enforcement of it. First, ANY question on law needs to include your general locale as laws vary by area.
However, in the US and most other countries, only a court can terminate parental rights. Courts are VERY reluctant to do so. Especially in a case where the parent is just not exercising those rights.
You may find this sticky helpful:
https://www.askmehelpdesk.com/family...st-116098.html
If you want to explain more about your situation, we may be able to help further.