Vehicle fraud

[Dave A]

How much did he pay for the bakkie?
What amount is in arrears?

Probably the right question to start off with.
At the end of the day you'll be chasing the seller for one or the other, so it does matter.

But first, let's run over what you should have done - and then pick up the pieces from there.

When there is outstanding finance on a vehicle, have the seller give you the settlement letter from the bank, and settle the bank directly.
(Make sure you print/get a proof of payment to satisfy the seller).
Pay the purchaser the change from the purchase price.
If they claim there is or was no finance, they must provide you with the logbook. Check that the owner is the registered owner and the titleholder.

From the transfer of ownership point of view, it is important to note there is the registered owner and the titleholder.
On financed vehicles, the titleholder (the bank) will have the logbook.
Once the bank has been paid, they will release the log book and the transfer of titleholder form (all duly signed in the parts they have to fill out).
The seller will have to fill out the owner part (somehow car dealers have been known to get around this - just sign it themselves I suppose).
The seller must also fill out their part of the transfer of ownership form.
You will also need a certified copy of the seller's ID book.
As the buyer, fill in your part of the transfer of ownership form.
Take the logbook, the transfer of titleholder form, the transfer of ownership form, the COR certificate (if applicable), a certified copy of both the seller and buyer's ID, and cash to cover the transaction fees to the motor licencing bureau and cross your fingers.

Now, given where your brother is currently, he either loses the vehicle and ends up trying to recover the purchase price from the seller, or
He "lends" the seller the money, settles the bank, and hopes the seller repays him one day.
Which is more viable depends on the numbers, but whatever your brother does, don't get soft on the details of the transaction this time.

Do it as I've outlined above
+ get a signed and witnessed loan agreement in place (consider using a lawyer for this)
+ secure whatever security you might be able to leverage
+ remind the seller that one of your options is to press charges for fraud.

Firmly securing the seller's favourite body part in a vice until your brother has been paid up would be a richly deserved bonus, but possibly not practical.