Welcome! Thank you for your question.
It is not legal for them to change the locks and prevent your entry. Your younger brother is the authorized representative and should be in control of the house and contents. He needs to qualify as executor with the probate
court. Once qualified as executor then your younger brother can (and should) force your older siblings out to secure the home.
If your younger brother refuses to secure the home and other assets then he is in breach of his fiduciary duty as executor. You can petition the probate court to remove him as executor. Please note that the court will have to appoint the named successor executor as the new executor if he is removed. You may find that you get an executor that could be worse if the successor executor is not someone you like.
I cannot provide you with legal advise. I have provided you with information about the law related to your question. My answer, and any information that you find online, should not take the place of having a consultation with a lawyer in your area to advise you regarding your specific issues.
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