You might as well appeal its free? i think. I think if your going to include your Brother and wife as co-sponsor a sworn affidavit by them would make it sound stronger.
I would also break down your disposable income you have available to you including the money you send to your wife and the money spent on trips, as this is available to you if she was here. If your self employed do you use an accountant? If so you could maybe seek some help there also?
good luck!
