This might be perfect! I've got myself, my wife, my mom and her boyfriend on my family plan, and my brother about to join us. His wife didn't want to jump on board, so we were paying around $54 per line after my discount.
My sister and her husband are also on Sprint, so if we bring my sister-in-law on board, and my sister and her husband, all with unlimited data, we've got a total of 8 lines, so we're paying $45 per line, plus taxes and fees?
I think that ends up cheaper for everyone PLUS, they can call get billed in their own little group instead of me paying monthly for everyone and then getting paid later individually.