Replying to IPhone plan question

I might plan on getting an iPhone, i am doing research about it, all the pros, cons, and everything inbetween.  I do have one question though.                                                 1.  If I do a family plan with my family once our contract is up, which is soon, will I not be able to get an iPhone if other family members get other phones? since the plan is different?  I dont think the rates apply to both but im not sure.  maybe you guys know for those of you who DO have one.  Thanks