You'll need to retain an experienced probate attorney to review the will and its interplay with the provisions of New Jersey law with respect to after-adopted children (and, in this case, grandchildren). Without reviewing the will's terms, it is impossible to answer your question. Good luck to you.
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I agree that you need to have an attorney review this. It is unlikely that anything happening after the death of your father-in-law would have any affect on the distribution of the estate. The Will could possibly provide otherwise. An attorney should be able to answer this question in about 5 minutes after reviewing the Will.
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You need to have a probate attorney review the will and facts of the case. Based on what you state in your question it should be clear from the will what should happen with the distribution of the property. Whether the executor is correctly administering the estate is of course another matter entirely.