For identical twins, it still depends on the time of the split of fertilised egg. (shrewdmommy.com)
It's not clear why a conquering male might refrain from destroying existing eggs, although they might offer eggs fertilised by the new male a better chance of survival if a predator attacks the nest. (newscientist.com)
While sperm stem cells have two sets of chromosomes, mature sperm capable of fertilising eggs have only one set. (newscientist.com)