How does the (T-Mobile) cell phone family plan work?

[Tai Chile]

i would like to know how the family plans work because i am thinking of getting one for my family with 3 lines but i would like to know how it works like does the family plan cover for all the lines like say i chose the tmobile family plan: 750 minutes+ unlimitted text for $69.99 for the 3 of my family, is there going to be just 1 bill a month for 69.99 for all 3 of us or is it $69.99 for each of us?? please help answer!!