question about using a phone from someone else

Hello everyone!! I have a question for you.

I am due for a new phone, but not due for a upgrade just yet. I still have another 5-6 months before I can upgrade. My question is, if my brother (on a total different account) has a upgrade available, but doesn't want to use the line or need the new phone. Can he still get the new phone using the discount and then I use it on my account (separate from his) or does that not work?

Let me know if what I asking doesn't make sense and I will try to explain it better, ha... lol

Thanks, CJ