Despite you or your brother posting this as a stolen vehicle, which it isn't...
Was the Jeep recovered in functional condition, or not? IE, did the kids leave it behind when they ran out of gas or broke down,possibly travelling with someone they do not know, or simply park it and walk away from it, likely after meeting a friend to travel with? Is there any reason to believe they were NOT the ones who left the Jeep halfway to Tennessee on I-81, nowhere near the suspected route to Ocean City?
You want help, more info would be kinda useful here. I do agree that after almost a week, there is cause for concern.
It certainly doesn't look like they are headed to Ocean City.