If your uncle died with no will or other testamentary instrument, he died intestate. Washington law sets out an order of succession of persons entitled to inherit when a person dies intestate. In your uncle's case, the next group who could inherit from his estate would be his siblings. I suspect you will have to initiate an adjudication proceeding in Superior Court to obtain an order that your uncle did die intestate and to name his heirs who are entitled to inherit.
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No probate may be necessary, depending what assets he had at the time of death, and neither you nor anyone else has an obligation to initiate probate. That said, however, if there are assets, it will be to someone's benefit to initiate intestacy proceedings. Typically, a lawyer will collect his fee from the assets of the deceased. Family members have nothing to lose, and everything to gain, by contacting a probate attorney and seeking advice. I strongly suggest that you, or those who would benefit from this estate, speak to a lawyer.
If your uncle has no spouse, children or parents, under the laws of intestate succession, the siblings would be the next group of relatives to benefits from the decedent's estate. At this point, your next step should be to consult with a probate attorney to have intestacy proceedings initiated, if there are assets. If there are no assets, it may not be worth the effort.
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