A Question about AT&T Data

My mom got an unlimited data plan with her 3GS, and still has it (even though she has a 4s now.) I am on a family plan with her, and got a 2GB plan when I got my Samsung Captivate (about a year ago). I have since imported a Galaxy Nexus. However, my friend is also on a family plan, and his little brother recently got his first smartphone (an iPhone 4s). He has unlimited data, because he shares it with my friend, who also has unlimited data because his first smartphone was a 3GS. Is there a way for me to get unlimited data, since someone on my plan has it as well?