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If this person has been granted custody of the child then yes the parents will be required to pay child support until the child is the age of majority in that state.
The age of majority in PA is now 18 or graduation from high school whichever occurs later (23 PA CS section 4321). It does not occur automatically.
If they have physical custody of the child (He is living with them) then yes they can file for child support for the child.
You have the right to try and get him emancipated. This would prevent the issues with child support. The main problem I see with getting this approved is he has quit school and had trouble in the past. The courts prefer to only grant emancipation to a child that has shown he is cable of caring for himself. Living with friends and not getting stable will not show the courts he is mature enough for emancipation.
Here is a link with further information on the subject:
Emancipation of Minors - All US States
The job will help to show he is self sufficient but is not reason enough to grant a emancipation. Keep in mind even irresponsible children can find a job. In the end it will be up to the judge to decide if the child is stable and mature enough to grant a emancipation.