If you want to stream on twitch you have to be at least 13 years old or be under the supervision of a parent or guardian. Please note the following from the Twitch terms of service:
"Use of Twitch by Minors and Blocked Persons
The
Twitch Services are not available to persons under the age of 13. If
you are between the ages of 13 and the age of legal majority in your
jurisdiction of residence, you may only use the Twitch Services under
the supervision of a parent or legal guardian who agrees to be bound by
these Terms of Service."
So this is pretty straight forward, only 13+ or with a parent for streaming and using Twitch.