What are a beneficiaries rights if they are not notified of the probate of an estate?

If you were a beneficiary you should have been notified of your inheritance.  You can go to the Probate Court in the county where he resided at the time of his death.  Once it was filed with the court, it would have become a matter of public record; accordingly it can be viewed by anyone (for a small fee.  However, you should be aware that even though there was a Will, a parent may disinherit their child.  Children typically have no right to inherit anything from their parents (although, as a general rule in such cases, there should be specific disinheritance language in the Will).  Additionally, some assets can be transferred outside of probate.  For example, if your father had a small estate, property may have been transferred by affidavit or otherwise.  Additionally, some assets may have been held as "joint tenants with right of survivorship", in which case the other joint tenant would have received your father's share to property operation of law.  In addition, funds in an IRA, pension, 401(k), or other retirement plan bypass probate and go directly to named beneficiaries (unless the beneficiary named was his estate).  The same holds true for any life insurance proceeds (and as to such proceeds, unless you were a named beneficiary.

If, however, you were a named beneficiary in the Will and the estate was not properly distributed, then you most definitely have legal rights and can pursue the matter.  From the facts presented, it appears that there has been a potential breach of "fiduciary duty" by the executor (your step-brother).  Fiduciary duty is the duty implied when someone is put in a position of trust to benefit other, such as that between an executor and beneficiary.  Accordingly, a fiduciary must at all times exercise good faith and put their interests second to the interests of the beneficiaries and/or estate.  Also, an executor owes a duty to exercise its obligations in accordance with the Will under which it was appointed.  Additionally, the executor must also follow the law as it pertains to the distribution and handling of estate assets.  The failure of a fiduciary to perform their duties may give rise to a claim.  At this point, you should contact the probate court in question and/or consult directly with a probate attorney.  Among other things, you will then need to have challenge any transfers and transactions that may have been made which were not in the best interests of the estate (and get the money refunded), and move to have an accounting of the estate.  If your step-brother, in his capacity as executor, is bonded (insured) you may also be able to go after any insurance money to recoup losses, if any.