You should submit this question to the NJ bar exam. The short answer is maybe, he may have a claim but it is all dependant upon the wording of the Deed and how all of these people took ownership. If they were joint tenants with the right of survivor ship then they would technically have no interest after each person died. if they took as tenants in common then you have a major estate issue going on. A review of the Deed would help answer this question. I suggest you consult with an attorney quickly because a transfer of the property in the future may get tricky and you will need all death certificates. Good luck
IMPORTANT LEGAL NOTICE: The response to the question posted is not legal advice and it does not create an attorney-client relationship. The response is intended as general information based upon the facts stated in the question, and is provided for educational purposes of the public, not any specific individual. The response given is based upon the limited facts provided by the person asking the question. To the extent additional or different facts exist, the response might possibly change. Responses are based solely upon New Jersey law.
It is not possible to provide an answer to you, because some very important information has not been provided. How was the deed drafted? Do the any of the named parties have a life estate? Do the named parties share as tenants in common, or by the entirety? Only after those questions are answered, will you know if you have to look to one or more wills. You should speak with competent counsel, or in the very least have a title search completed.
As the other attorneys have indicated, the answer to your question is dependent upon the wording of the deed.
If the deed states that the parties had a "joint tenancy with a right of survivorship", then the son of your deceased great uncle and aunt may not have a claim. He may be disinherited.
However, if the deed does not include the "right of survivorship" language, then he may have inherited his parents' share of the property.
This answer is for general education purposes only. It neither creates an attorney-client relationship nor provides legal guidance or advice. The answer is based on the limited information provided and the answer might be different had additional information been provided. You should consult an attorney.