If you believe that your sibling has engaged in criminal conduct (i.e. took cash for personal expenditures, opened credit accounts in the parent’s name for personal use, cashed life insurance policies, etc.), you should contact your local police department concerning the issue.
If you wish to recover such funds, or attempt to revoke the Power of Attorney, or to work to adjust any long-term family estate issues, we strongly suggest you find a qualified local attorney to help you with your situation; you can find one for FREE at Standard Legal’s Attorney Finder page.