If any of the lines are still under contract, then you would be responsible for the Early Termination Fee (ETF) for those lines if they are cancelled prior to the contract being completed. You would need to call Verizon Customer Service or go to a Corporate Store in order to cancel. You cannot do it online.
The ETF would be $175 for a regular phone or $350 for a smartphone minus $10 per month of the contract that has been completed.
Your brother can do an Assumption of Liability (AOL) for his line in order to take it over in his name.
A line can be suspended for 90 days without billing and can be renewed for another 90 days without billing within a 12 month period. The amount of time that it is suspended without billing would be added on to the contract.
I believe that I line can be suspended with billing (meaning you/he keeps paying each month) for longer period (perhaps indefinitely).