It would be interesting in a case of a double yoker actually hatching twins,if both chicks born will be able to reproduce?? I know in the case of cattle when twins are born of the opposite sex,the female calf is unable to reproduce and called a "freemartin".This condition is caused by the male calf making testerone and because this hormone is created and flows between both calves,it renders the hiefer calf unable to be reproduce functionally. I'm sure chickens are diffrent and possibly the roo chick would not be producing this hormone while still in the embryonic stages inside the egg,,but if a case occured and those twin chicks could be tracked until maturitity,,,,wonder if the roo and the hen could be a propsective reproducers??