You might be able to claim the money with a simple affidavit of heirship, which would be relatively inexpensive.
Otherwise, an application to determine heirship would need to be approved by a court so that you end up with a signed judicial order. This would require the appointment of an attorney ad litem by the court as well. Although not a complex process, there would be more time involved for the attorney you would hire.
I would be happy to visit with you further to talk more specifically about the case based on the facts involved.