Push Notifications wont work on apps iPhone 3G

Hi guys,

            i have a problem that is really bugging me and that is one of  the features of the iphone which is the notifications. I realized that only when i physically tap apps like whatsapp or mail, will it then connect to its server and download it's mail or messages. My brother on the other hand(uses an iphone 4) recieves messages even when  his apps are 'offline'. This is really bothering me as i have to tap the app to actually know if i have recieved email or messages. Is there any solutions ? ps, other apps like twitter are not working too and i think that the problem lies with the notifications settings or something.

Your help would be appreciated.

Thanks