Sprint Family Plan Question

[DerfBWH]

Hi guys, not sure if there's an answer to this yet but figured I'd ask anyways.
My family currently has the Sprint Unlimited Everything Family plan, and I'll be looking to add myself as a fourth line to this plan. They all have smartphones. Will I be able to simply go to an Apple store on launch day, purchase an iPhone 4S for Sprint, and get it added as a line to this plan no questions asked? Or will I be for some reason ineligible?
Thanks!

 

[Mhotep]

Should be able to add as long as you have account info. May need to to have main account holder to verify info.