Can I withhold or altogether disinherit my sibling's inheritance if he won't respond to any paperwork?

My mother passed away without a will. Under Alaska State law, she has what is considered a "small estate" and therefore there is no probate. My younger sibling (living in Oregon) signed a nomination to appoint me as administrator. My eldest sibling (living in Washington) estranged himself from myself and our mother over 10 years ago and has not signed or acknowledged receipt of the nomination. I don't know if the email or mailing address I have even reaches him, but since there is no will I believe I am legally bound to split our mother's assets (cash and personal items, there is no real property) equally between we three children, but if my sibling refuses to respond to anything, can I send a final, notary stamped, certified with return receipt letter stating if no response is received within xx days he will forfeit all rights of inheritance from our mother's accounts and belongings? Then just split it equally between myself and my younger sibling?