By yehuda we find that one child stuck out the hand before the other was born. A nice Halachic discourse can be given about which one are you Podeh, and how does this status relate to Ever Min Hachai and Ben Pikua. Does that hand still have a Din of Yerech Imo? What about the rest of the boy? By an animal, if you were Makdish the hand while it is out, is it Tofes the rest, according to those who hold that nomally it would? What about the mother?
Yehuda got Malchus, which was taken from Reuven. We see right there the concept of Pidyon, or of transfering a title.