I also have this issue. I'm on an AT&T family plan and splitting it typically even across the board except for that whoever does overages for calls pays for themselves. The problem I run into is when there is data overages since everyone is sharing the collective pool of data. (I have a 30GB plan with 7 people on it) One person will easily use up 50% of the data but then my parents will barely hit over 1%.
I also have this issue. I'm on an AT&T family plan and splitting it typically even across the board except for that whoever does overages for calls pays for themselves. The problem I run into is when there is data overages since everyone is sharing the collective pool of data. (I have a 30GB plan with 7 people on it) One person will easily use up 50% of the data but then my parents will barely hit over 1%.