Uh~

Today is such a nice day, there is no school, though we still go to school to do projects, there is not so much stress. My most headache practical report, AMFS protein gel report I had finally completed after researching for AGES at night.
My cousin who have been staying over at our house these recent few days either go out till late late or come home and face our computer, not us, the COMPUTER!.. Urgh...
When he came for the first day he was not too bad, but slowly he began to show his attitude already. Snatch with us for the desktop computer, not that I don't like him staying or anything but there is a chinese phrase saying : You give him a meter he takes a mile or something. We never ever refuse to let him use the computer but there is a time limit, others still want to use too. He use my lappy without telling me :X
My brother told him to ask me first before using (Because I told my brother he need to ask) but he ignored my brother. Then he take out the battery from the lappy and i dunno, so i just unplug the power supply but luckily my laptop is still fine.
But even if spoil I also cannot scold him or anything because he is my cousin ma, what to do?
Then if these arguments continue my granny will sure buy a new laptop especially for him. But that would mean that since the laptop is totally his he will never lend it to us, that i don't mind, but all the more he will face the computer all day.
I understand his situation, but when people lend him something can he at least be polite and not give a black face or complain when we want it back for our work?