Cerberus and GMAC

I was reading Forbes about the fact that AM Best is about to drop GMAC insurance rating down from an A- because they may have to problems with their mortgage division. So who is the majority holder of GMAC, Cerberus, who just purchased Chrysler? My problem here is how entwined are the big 3 I had no idea they owned all of one and the finance arm of another. I am now worried that if one fails will they all go down or will they try to protect each other and risk going down together. How much involvement is there among them? Also who owns the majority of Cerberus, I would bet the house of the rising sun is in there somewhere. Will do more research and write more on this later.