Hm... Seems that your brother is bored out of his mind, OP. If he is entirely done with his work, perhaps you should give him some more to occupy him (I suppose that would work better if your position is above his). If not, it might be time to report to a supervisor. Even if it is your sibling, there comes a time when professionalism is the most important thing to consider. Working in an office is just such a situation. Being fired for not taking his job seriously might get him to think twice the next time.

I used to work for my brother he did the same stuff >.<

Just another day at No 10 Downing Street eh?

That sounds like something I would do. x]

"Snuck" is not a word. The proper term would be "sneaked."

Perhaps he needs a lesson in revenge...

Why do you work with your brother?

Make it a prank week! As long as you get your work done, there should be no problem.

The duct tape part made me laugh ^^

google "office pranks" for ideas and fight back! office prank wars rule. here is a freebie for you. if his desk phone is black, get some black shoe polish and apply it to the receiver (part where you put your ears). then call him. then laugh but don't say why. see how long it takes him to notice - longer = funnier.