im on a family plan with my mom since like ... 2002. she's going to upgrade to iphone5 in a few weeks. i'm not 100 percent sure, but i ahve a feeling this will force my secondary line into the new terms of the shared data plan.
if it didnt, i would suck it up for another contract cycle and wait till there is a phone worth buying on vzw and get it off contract.
Your mom would loose her unlimited plan when she upgraded to the iphone 5. But I dont think you would loose you unlimited data even with being on the family plan,unless you upgraded with a contract.Thats the way it was explained to me