Much depends on the state in which your father died. If he died in Los Angeles, then California law requires that the original of his will be filed with the clerk of the Superior Court in the county in which he died resident. You may want to check the L.A. Superior Court's will files to determine whether his will has been filed with the court. If your uncle is still named as the executor of your father's will you might wish to ask him directly if he has filed the will as required. Even if your father used a living trust to do his estate planning, he should have a pour-over will, which would still have to be filed with the court. Hawaii law may have similar requirements, as to which an attorney who practices in Hawaii could advise you.
California law also requires that notice be sent to the beneficiaries of a living trust when it becomes irrevocable. Notice is to be sent to the current beneficiaries of the trust and to the persons who would be the intestate heirs of the decedent. Again, Hawaii may have enacted similar or parallel legislation; an attorney who has probate and trust experience should be able to advise you.
You may also wish to spend a little money and hire an investigator to attempt to track down your father's assets. You may need to open a probate of his estate in order to have you or one of your siblings appointed as a personal representative of his estate so that you have the legal authority to talk to financial institutions at which your father had accounts and get copies of records. If the accounts were closed out, there might be records indicating who was responsible for doing so.
Unfortunately, you've left your inquiries very late. From your question, the second wife died 2 1/2 years ago, and your father some time prior to that. This means the trail of his assets is growing very cold at this point. Unless you take action fairly quickly and energetically now you are likely never to find out what happened to your father's estate.
The foregoing response is not intended, nor should it be viewed as an attorney-client communication, nor shall it give rise to an attorney-client relationship. The response above is given in response to the skeletal outline of facts forming the question and might be materially different if all of the facts surrounding this matter were known in full. You should seek the advice of an attorney who practices in this area for complete advice.
If your father died in Hawaii, you should check with a local attorney about what rights you