My brother was given Power of Attorney of my mother years ago..since then he has been in and out of jail, recently she wrote a Living Will giving me basically everything she owns..the question is, does that stop my brother from taking everything and making the decisions? in the state of Washington
I'm assuming you know the general area in which your brother lives? If so, a notice can be published in a legal newspaper for a given number of weeks. It's not done so that a person can necessarily be located (most people don't read legal newspapers), but rather to comply with publication as a last resort method of notification when someone can't be found (if that makes sense!). An attorney could handle this aspect by sending a revocation notice for publication to the local legal newspaper.
But you still need to get a new DPOA drafted and change any joint ownership designations on accounts - ASAP.
The only problem I can see here is your brother getting money using his POA document if people do not know it has been revoked. You do need to let him know in a registered (signed for) letter that it is revoked. If he knows, attempting to get money or anything else would be theft. I hope that doesn't happen.
One warning I've heard often when it comes to appointing a POA is to make sure it is someone you trust completely. A dishonest POA can cause a lot of financial damage. It is illegal for them to do, but there are some who would do it anyway.
Make an appointment with the attorney who prepared the POA to see your mother and change the terms to remove your brother. Also inquire if your mother does have a will and if not request that one be drafted, or explore the option of holding assets in joint ownership with rights to the survivor.
As to whether your brother can usurp assets meant for you, that would depend on how those assets were held. AND! Whether or not your mom has a last will and testament naming you as the sole beneficiary. You know she has a living will. That's not what's needed. Does she have a last will and testament?
Find that out. See what it says. See how your mom holds her assets and you'll be closer to your answers.
If your mom wishes, she can revoke her son's POA. Or, if she never gave him a copy, she can just destroy the document. You should consult an attorney on mom's behalf for answers.