Restrictions.

I doubt that. Once an account has been created the age can not be changed. Nice try though.

Excuse me It was when the account was created.

An Xbox LIVE account can only be changed to an adult account after the account owner reaches legal adult age.

To change your Xbox LIVE account to an adult account

1. On your Xbox 360 console, sign in to Xbox LIVE using the account that you want to change.
2. Go to My Xbox, select your avatar, and then in the Account Management panel, select Manage Account.
3. Select Promote Child Account in the Your Information panel.
   
   Note Promote Child Account will only be available if the date of birth for the account indicates that you have reached adult age for your country or region.
   
   
4. If you are prompted to sign out of a current game session, select yes.
5. On the Promote your current Xbox LIVE child account to an adult account screen, select Continue.
   
   Notes
   • If you are a member of an Xbox LIVE Family Pack subscription, you will also be removed from the Family Pack by making this change.
   • Steps 6 through 9 apply only to accounts that are currently billed to a credit or debit card. If your account has a prepaid subscription, go to step 10.
6. On the To promote your account, replace the credit card that is associated with the account with a new card or payment method screen, select Continue.
   
   Note The same credit card can be used again. However, the credit card details must be re-entered.
7. Enter the name, credit card type, credit card number, expiration date, and verification code for the replacement credit card, and then select Next.
8. Enter the billing address, city, state, and postal code for your credit card, and then select Next.
9. Verify your contact information, and then select Done.
10. Accept the Xbox LIVE Terms of Use and the Privacy Statement.
11. On the Your Xbox LIVE account is now an adult account… screen, select Done.
    
    Note If your Xbox LIVE account does not change to an adult account, try signing out and then back in again.

Bottom line is you can't. If the information was not correct when the account was created then it was/is against the CoC and ToU. The best reply I can really give you is; If the account birthrate is in fact incorrect talk to the person who set it up. They may be able find out how to fix this for you. I don't think anyone here will do much. The reason being is there are many children who come on here wanting to change their own settings with out the adults knowing about it. You wont find many here who want to be responsible for anything like that.

I know that, I just don't believe it was your family that made the mistake. I believe you entered the correct information and now you realize by doing so it limits what you are actually able to download/access via the Marketplace. You don't like that and are trying to find a way around it. There is no way around it short of creating a new account and starting over, but that would require you to lie about your actual birthdate thus voiding the digital contracts you agreed to and could result in enforcement action being taken against the account. It doesn't happen very often, but there is that possibility.

BTW those limitations are there for a good reason. There are certain guidelines and laws that even the almighty MS must adhere to.

Well I figured it out by promoting the account thanks everyone.