That would be inappropriate.  The trustor/settlor may not properly serve as the trustee of an irrevocable trust that he/she has created (although I cannot speak with specificity about Washington law).

I assume "trust account" means a bank account owned by the trust.  Correct?

Sure, it's possible.  However, assuming that "disbursed inheritance" means money that the older child received from the trust (which is not technically "inheritance"), I'm not sure (a) why you think that might be an appropriate thing to do, and (b) why you would think the state might do this (although it's not beyond the realm of possibility if no one steps up to have the parent removed as trustee).

Not really sure what you're asking because neither of these are complete sentences.

Sounds like you have quite a mess and would be well-advised to consult with a local attorney for a review of the situation and advice.