Enforce Password Change & Maintain one password for Multiple Accounts


I would like to know if there is a way to ENFORCE a password change for the user and also is there a way we can make a password expire after say like some number of days.

Also I would like to ask that if there is any way to maintain one password for multiple accounts, like we are using 3 accounts and more or less the userids are similar across all 3 accounts.

Is it possible to have one data bank of the userid and password so that if we change the password in one account then the password for the other accounts is also changed with the same one.