1st private money borrowing for short sale

[Gerardo Escutia]

Hi guys, 

I am in the process of putting a bid on a short sale home. This year I purchased 3 buy and holds, so I am running low on funds. I found a great deal and do not want to let it pass. My brother and brother in law are willing to lend me the money to buy the property cash if I was win the bid. 

But I am having trouble as to how to show proof of funds since the money is not going to be coming from me directly. What is the best way to show proof of money. What documents do I need to show when I submit the bid. 

Please advice as to what is the general process when putting a bid on short sale when borrowing money from family.