No Contacts Showing up in Mail gmail account iPhone 3G

Hi,

     Me and my dad both have the iPhone 4. I previously had an iPhone 3GS and I set my email (gmail account) up as an IMAP because there was no quick link to gmail set up at that point in time. The way I set this up carried over to my iPhone 4. When I compose an email, in the To: field, if I start typing the email address of someone I have sent an email to (either on my computer or on my phone) or received one from, their address will pop up. My dad also uses the mail app (gmail account) but his addresses won't pop up in the To: field. His is set up from the quick set up for gmail when you add a new account, but I also tried setting it up as an IMAP account the way mine is on my iPhone but they still won't pop up. Were both running the same iOS 5 software and everything. Does anyone know why his mail app isn't working the same way mine does? Any help is appreciated. Thanks.