It is not important when the law came into effect barring felons as estate representatives, what is significant is that administration of the estate has apparently not been completed after 25 years, and that would ordinarily be more than enough by itself to remove an administrator.
I don't have a McKinney's statutes book here and you can check one at a public or law library, but the Surrogate's Court Procedure Act (SCPA) was codified in 1961 from previous statutes and Section 707(1)(d) prevents a felon from serving as an executor or administrator of an estate, and it's likely that provision was in the original SCPA, if not earlier versions. A broader provision allows a Surrogate to refuse to appoint someone as a decedent's representative for non-felony crimes or acts evidencing "dishonesty" as well. http://bit.ly/16ZELSe
But Mr. Miller's answer is spot on that your removal probably has little to do with your criminal record, whether it was sealed as being committed by a minor, or whether you can get a Certificate of Relief from Disabilities. It simply has to do with your negligence and lack of diligence in wrapping up the estate in a timely manner, collecting the assets, paying the just debts, distributing the remaining corpus of the estate to the legatees and filing required tax returns and accountings to the Court. Normally, that's supposed to be wrapped up in a fairly quick timeframe, a year or two, not 25 years.
By the way, after the filing of the final accounting with the Court, the Letters Testamentary or Letters of Administration issued to an executor or administrator expire and that person has no further legal powers over the estate.
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