The babies look great!  Somehow I missed when you posted about twins!  Congrats!
As far as the speculation about whether or not twins would be likely to produce twins... I have no idea.  But if it works like chickens, then a female that has produced twins is likely to do so again.  Well...that's assuming a yolk in a chicken egg = a possible embryo if she'd been with a rooster.  Used to have a hen that laid double yolk eggs more often than she did regular ones, and her record was 4 yolks in one egg!