title_body: Transferring files from one Kindle to another with a forgotten password
upvoted_answer: You don't need to worry about accessing the old kindle. Everything purchased through amazon remains available from the cloud. Presumably your cousin used the same Amazon account to purchase both kindles.  Just log on and send it to the new kindle.
  
  If not, go to amazon.com click sign in and than go through the forgotten password process for the original Amazon account. The password for the old kindle may be different and does not matter, it is only the account that matters.
  
  Once you have access to both accounts, you will need to transfer the new kindle to ownership of the old account. Then you will be able to download to from the cloud as you learned in your earlier research. 
  
  Alternatively you can keep the accounts separate, after you have accessed the old account, you can download to the PC and transfer to the new kindle, but this will only work for non-DRM works.  DRM works will be restricted to devices registered to the original account.