disable sharing

Hi

Could someone please help me because this is driving me crazy

I've used an iPhone 4S for a year already, but my bro recently got an iPad 4 and I dont know why but we have shared contacts/calendar/alarms and possibly even photos. But my biggest problem with this is whenever I set an alarm, it goes off on his ipad and not my phone, same with alerts on the calendar. What do I have to do to get rid of this 'feature' because currently it is nothing more than pure annoyance and i'm really on the verge of switching to HTC or Samsung, I know we share the same itunes account but there should be a setting to disable and i've scoured the entire itunes for disabling that and i just cant find it.

So could someone iGenius please help me resolve this issue?

Thanks in advance