The main problem here is the parents being illegal immigrants and if they file an action in the court, which they have the right to do, they will likely face deportation from the US and the court will not rule on the guardianship. This is going to require an immigration attorney first to try to deal with the illegal immigration status before anything. If the immigration status cannot be handled, then the parents would not be able to file for the guardianship and there would have to be another relative who is over 18 who would have to apply for the guardianship in the court and file a petition for guardianship over an adult in the court. If the immigration issue can be handled, then the parents can apply for the guardianship in the same manner.
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