That is the least of your worries. everytime you call customer care or chat or go to a sprint store they will always pull up the old information on your account. that really ticks me off because i keep thinking why the heck is Sprint keeping my old information as current? i used to have a line with my sister under an employee discount but now i made her fill out a transfer of liability form and just till last week i found out that my sprint pcs id name and called id was under the old account holder's name- thats weird because i bought a new phone on the same day i openned a NEW account under my name.
so don't worry just go to a sprint store and fill out the transfer of liability form with the old account holder present and with his or her id with them.
You will have to have your sister and boyfriend together and call Sprint or visit a sprint store and they will transfer it over, There will be no charge if your boyfriend's account is eligible for more then one line, But if his credit score is low they may require a deposit.