I haven't read the whole thread but just wanted to add my two cents regarding this. My two are from the same parents and are on completely opposite ends of the spectrum in almost every way, so I totally agree that even within litters there can be huge differences. Riley is a very difficult dog, inheriting almost all of the 'negatives' it seems. DR, doesn't like strangers, prey drive through the roof (especially for real animals), but very low confidence and very easily stressed. If you are a part of his family circle he loves you but it takes a very long time to earn his trust. Aura is near perfect in comparison and could easily make a nice companion/pet if that is all she was offered. She loves everyone, human or animal, and I don't think she would ever bite in defense. She still has the high energy but is easily satisfied with balls/toys and any attention you want to shower on her.