There are many reasons why parents might leave their children in the care of grandparents. Perhaps you had to step up and start taking care of your grandchildren when your child got arrested and then later convicted of a crime or had their rights terminated by the state.
Perhaps your child has struggled with addiction or mental health issues that have left them unable to fulfill the obligations involved in parenting. Some parents will even abandon their children, asking their parents to babysit and then leaving and refusing to come back or communicate with the family.
Regardless of how you wound up caring for your grandchildren, when your child or the other parent shows up, you still have rights. You could request visitation or even ask for custody of the children you have invested so much time and love in raising.
The Pennsylvania courts sometimes agree to third-party custody arrangements
Most of the time when families have formal custody arrangements, those arrangements only apply to the biological or adopted parents of the children involved. However, Pennsylvania does recognize that third parties, including grandparents, can sometimes also play very important roles in the lives of minor children and even serve as parents despite a person having no formal parental relationship with the kids.
If the children have lived with you for some time and you have stepped up to fill the role of a parent, you may be able to hold yourself out as someone who has fulfilled the obligations of a parent and can possibly request shared or primary custody of the children.
Especially in circumstances where you worry about whether the parents attempting to regain their parental authority can do so in the long term, requesting formal custody or even initiating a grandparent adoption could be in the best interest of your grandkids.