It sounds like you need to ask your family member to complete a change of ownership to your name @zt04 , this would give you control of the contract and monthly payments.
Ask the family member to complete this form Change of Ownership when this has been authorised, you will need to accept the contract into your name, this will be subject to Vodafone's credit checking criteria. If this is an Evo contract, only the airtime part of the contract, can be transferred, the device part of the contract is a credit agreement.
This other alternative will be to ask Vodafone to split the account, this will give you access to the online account and making the monthly payments but with the family member still be responsible for the account.
Vodafone have a three month clear payment policy, when the three months have cleared, you should be able to add additional numbers to the account.
