Your seemingly simple question is more complex than you think, and is actually several questions in one.
Who pays the loan?
This is easy. You can pay the loan to help your brother by simply writing a check each month or setting up the automatic payment method of your choice. If that's your motivation, any number of methods will work fine.
The lender doesn't care who pays the loan. They only care that it gets paid.
Who can use the account?
Again, very easy. Your brother could make your reservations for you, but a much better approach is making you an Associate Member as Michael suggested above. Easy to do, easy to undo -- both can be done online. You would NOT receive DVC member benefits in that situation, but would be able to use, bank, and borrow the points.
Who OWNS the account?
Critical question, but also relatively simple to set up in a variety of ways. If joint ownership is desired, your name could be added to the contract provided there was no encumberance (loan, lien, etc) on the contract. If your sole ownership is desired, as long as there is no encumberance that's a simple matter of a title transfer through MS. Between family members, it's no big deal.
Ownership, obviously, determines who can sell the account. If jointly owned, both would have to agree and sign. If he owns it, it's his decision. If you own it, it's your call.
Likewise, ownership determines who is responsible for the ongoing financial obligation until 2057. NOT a minor detail.
Ownership also carries benefits others have mentioned, but those are not guaranteed and are not a big deal in the grand scheme of things.
But what about the long-term?
Aye...there's the rub! The cost of DVC ownership has two components: acquisition cost (purchase price, loan, etc) and annual cost (In Disney's pixie dust terminology -- "Annual dues"). Over time, acquisition cost is a fraction of the cost of ownership -- the much bigger cost is the annual cost of "dues."
AKV has the highest "dues" of any WDW DVC resort: $6.30 per point in 2015. So for 160 points, that's $1,008.00, and it will almost certainly increase a little each year.
If your motivation is obtaining DVC points at a discount, you have to consider whether what you save taking over payments outweighs the high annual dues at AKV.
Depending on how long you own, another resort with lower annual dues, purchased resale, might have a lower total cost. But you'd have to find a specific contract and compare the exact costs to know.
Good luck with your decision.