At level 1, you can have up to five team members. Starting at level 10, your maximum number of team members increases to six. For each even-numbered level following, your maximum number of team members will increase by one. You can have a maximum of 50 team members at level 100. Further leveling does not add more team member slots.
If you remove a team member, you lose that 5 attribute points from your energy, attack or defence. Points removed from this function are taken from your highest stat. When you re-add another new team member, you re-obtain the 5 points. Keep in mind, however, that if you remove more than one team member within a 24-hour period, you will be charged an additional attribute point penalty (for a total of 6 points lost) for each subsequent removal, while only being able to gain back 5 when you add a new team member back, resulting in a permanent attribute point loss.