I agree that temperament is hereditary. My Chihuahua Nina's father had a very aggressive temperament and my girl is identical to him; so are her siblings (all 6). Although I have nurtured her and truly treated her like a princess, she still shows extreme dominance etc. I will ad that should we not have treated her the way we did; she would probably be way worse. On the other hand my 2 other chis parents were very sweet and loving; they both are identical to them and combined with our nurturing they act like babies.
Sometimes the smallest things, take up the most room in your heart......