How to overcome 'incorrect password' in microsoft family when using correct password?

This has happened to me as well, i am using the correct password, but keep getting the same message. Incorrect password.

Hello there!

Please make sure you are using the correct e-mail and password. I recommend plugging in your keyboard to your XBOX 360, and typing in both your email and password slowly and carefully. Passwords are case sensitive, so if your password was 'Password', but
you typed it like 'password', then it would say it was incorrect.

Hello Iceman,

This error occurs if an incorrect Microsoft account (formerly Windows Live ID) email address or password
is entered when you add a secondary or child account to a Gold Family Pack. For instructions about how to add the child account, enter the parent’s Microsoft account, see Add
or remove Gold Family Pack members.

Let us know how that goes, or if you have anymore questions.

If it's asking for a login email and password when you try to purchase Gold, you may be operating a child account with parental controls in place preventing you from making the purchase. The reason it's not telling you that you have an incorrect password
is because the password is correct. The problem is you're using the child email and password to authorize itself to make a purchase, and that's not going to fly. You need to enter the parental email and password.

According to the family pack FAQ page, that error means the WLID and/or password is incorrect when being entered, though
it seems you can verify it's correct since you're able to sign in on your brother's account on xbox.com successfully.

Try clearing your browser's cache and cookies, or using a different browser when using
the steps on xbox.com.