From what I heard a number die and a number of them hatch. However, it would be wiser to slip another birds eggs under them for them to raise so the young wouldn't be unhealthy. I'm not an expert on this, that is just what I've read. I hope it helps.
Society finches are monogamous, though males may breed with other females (I'm not sure). However, they remain in the same pair for life (I haven't keep any, but I did keep zebra finches).