I have a 2 year individual plan with Tmobile, can i change my current plan into...

...Family pland? my boyfriends is using an individual plan with tmobile for 2 years. Now, he wants to change it into family plan to add me as an extra additional line, can he do so before he completes his current plan? if he can , does tmobile charge he any thing?
what he has to pay for tmobile to change the plan

no he can do it without extra charges... besides what the plan actually costs.....