Ahhhhh I see!
Did he take the finance out in his name to help you out with the understanding that you would still make the payments?
Legally, it's in his name and it is up to him to make sure the payments are met on time, if a payment is missed, it wil be him that will be chased, not you.
You could ask him if he wanted to take over the payments, but if he doesn't then you have 3 options.
1. Give him back the car anyway and leave him to make the payments whether he likes it or not, but that's pretty nasty.
2. Sell the car, settle the loan and neither of you need to talk about it again.
3. Make up with him and restore harmony within the family :)
I've just remembered something too, a couple of years ago my pal broke up with her long term boyfriend. They had taken a loan out and they were both putting money toward the repayment, but the loan was in her name.
Anyway, when they broke up he decided not to continue paying his half of the loan thinking that he'd be free from it because his name wasn't on the loan agreement. My friend went to a solicitor who instigated something that forced him to pay his share.
I'm sorry I don't rememer the ins and outs of it, but it's worth remembering when you make a decision about what to do.