How can legalize the fact that you are the sole care giver of your aging parent? is there a process to follow and what is that process. can you make it retroactive and is there a statute of limitation?
Become their guardian. It requires a Court Order.
You have to file a Petition for Guardianship.
You have to petition the court for Plenary (Full) guardianship over the person and property of the ward (your parent)