How do you change ur age on xbox live?

i am 19 and my 7 year old little bro wanted an xbox live so i made one and he hated it. so i am using his and i wanted to buy some extra content for call of duty, and it said %26quot;this is rating is blocked for ur age group%26quot; cause i entered my bros age, how can i change the age?How do you change ur age on xbox live?you cant, which sucks. you either have to wait 11 years to buy that extra COD stuff, or make a new profile.