As i turned 18 not to long ago i suspect it comes from my account being connected to his credit card in the iTunes store,
Yep, I agree that his name on the iTunes account is in use during your dev registration attempts. You apparently need to try change the basic iTunes account information, either by getting rid of that one and establishing another one with your name, or by changing the billing information on the account as it exists now.
If you go into the iTunes application and click on the user name, top right and log in, you can see a summary of active account information.
Is the name in use when you try to register as a dev, the same name that is on that account?
Can you update the account with your valid name and c'card info, etc.?
Have to ask if you carefully reviewed the dev signup requirements to confirm you can satisfy them going forward etc.
iTunes customer service is here:
http://www.apple.com/support/itunes/
...perhaps they can help you determine the shortest route, etc.