What are the Pros & Cons of adding someone as a authorized user to one of your credit cards?

I just started establishing credit not that long ago, but I have 3 credit cards and a Macys card. I been making my payments on time and everything is going well. My brother, has bad credit due to some poor choices he made a while back. He can’t even get approved for a card really. So he’s asked me to add him on as a Authorized User to one of my credit cards, but when his card comes in the mail to Destroy it. He won’t use it and doesn’t want to use it, he just wanted to be under one since he has no way of building credit so I can help him. (He bought his car outright cash so he can’t even do that to help his credit)
Now I was wondering, what are the Pros & Cons of adding my brother?

Remember, he is not going to use the card, he just wants me to help him help his credit.

Thanks.

Tags: Authorized, Cards, Cons, Credit, Pros, Someone, User