Lines under one account work independently of each other.
In other words, your brother has 1 line under his account right now.
Ask him to order the Pixi, go to the Verizon store (ask your brother to go to a Verizon store), and add a line to his account (with your Pixi). This will not affect his line, and he will still be able to cancel it by paying the ETF for his phone. His ETF would be no different whether you added a line to his account or if you didn't. Once he cancels his line, the whole account gets transformed into a individual plan instead of a family plan (Makes sense, right?).
Then I believe you will be the owner of the account (well you're going to need to call Verizon to transfer the account ... or whatever Verizon has to do ... but you'll be fine).
well is transfering the account easy? I mean he is in SF I am in LA. It would be a total mess up if he had to come or I had to go.