Mr. Lucas is correct. This is where a Durable Power of Attorney is useful. If your mother (while she had capacity) granted an agent the power to modify or revoke the trust they have the power necessary to appoint you as trustee. The authority to deal with trust property and to revoke or amend the trust is a fairly common power granted in a durable power of attorney. Find out if your mother granted any person such a power through a properly executed durable power of attorney.
Are there any other Estate Plan documents? For example, she could have a Durable Power of Attorney that appoints someone to amend/revoke Trusts, in which case the successor trustees could be amended. Absent some other document like that, then we have to look to the terms of the Trust itself. If it's B of A and Interstate CA, then there's not a lot to be done. If you have reason to believe she wasn't competent when the Trust was executed, that could also be a grounds. You should have a qualified Estate Planning attorney at least look over the Trust and other documents for you to see what the terms of those documents are and if there's any way to accomplish your goal.
If the terms of trust or other estate planning documents do not provide a mechanism for selection of a successor trustee under the circumstances your only option is to petition the probate court for appointment.
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If I recall correctly, First Interstate was bought by Wells Fargo. Wells Fargo would then be the successor. Both Wells and B of A would have to decline to serve. As stated, you would need to look to the provisions of the Trust to determine how to appoint a successor. If there are none, a Petition can be filed. You really should consult with an attorney in the Valley or the city for assistance. Your Petition would be filed in Downtown LA.
Also, as indicated, if there is a Person appointed as your mother's agent under a General Power of Attorney, depending on that document and the Trust, the agent may have authority to amend the trust and name someone.
Again, you really need to consult a Trust/Probate attorney.
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