It looks like you want to upgrade his account to a master account.  You can find the [details on how to do that here][1], but quoted here are the steps below: 

**How to upgrade a sub account**

Sign in to the sub account using Playstation Network sign in details:

**PlayStation App**
Tap the PlayStation Store on the home screen and go to  [Online ID] > [Account Settings].

OR

**PlayStation Store**
Go to PlayStation Store. Sign in, go to your Online ID at the top of the page and click [Account Settings].

OR

**Account Management website**
Click here and sign in for the account management site.

 1. Select [Upgrade Your Account] on the Dashboard.
 2. Read and agree to the SEN Terms of Service.
 3. You may need to sign out and sign back in to complete the process.
 4. You now have a master account


*Notes on this change:*

-Sub accounts can be upgraded using a web browser or PlayStation App.

-Sub accounts cannot be upgraded through Account Management on PlayStation systems.

-Upgrade to master account is permanent. The account cannot be changed back to a sub account.

-The master account to which the sub account is linked cannot stop a sub account from upgrading.

-Parental controls will no longer be active once the sub account has been upgraded.

-Any pre-orders placed by the sub account but not paid for from the master account wallet before upgrade will be paid for from the new master account wallet.

-Any new purchases and subscriptions will be paid for from the new master account’s wallet.

  [1]: https://www.playstation.com/en-au/get-help/help-library/my-account/access-and-details/what-to-do-when-a-sub-account-holder-reaches-18/