Help me get my account back

My account got stolen last year and every time i try to recover it, i'm denied due to "insufficient information" although i'm giving accurate information about the account and i am the owner. it was originally my brother's account on xbox 360 then he gave it to me when we got our original xbox one. i'm using the same xbox, with the account still logged into it, and they won't verify the account as mine. please help me get in touch with support because it's been a nightmare to recover my account.