According to Terms and Conditions it sounds like it's not allowed. If it's just you and your brother and you live in the same house, I personally see nothing wrong with that. You can set up a user on both PS3's with the PS+ account. Go to your account settings and activate the system on both consoles for game content. Only one console will be able to sign in at a time with the PS+ account, but you will be able to download and play all PS+ game content to both. You can only activate two PS3's for game and video content per user account.
Hope this helps.
If me and my brother wanted to get playstation plus could we share it between our 2 ps3?
If one of you is a sub account of the other you'll be able to share the games. Only the master account will have access to the cloud and auto update. That's perfectly legal. My daughter shares my content. Other than that if you're both master accounts you'd both have to get a plus membership. It's impossible to share otherwise.