If you're not going to read then stop spouting incorrect shit lmfao. Temari and Kankuro were not raised with Gaara.
Neji is arguing destiny. Destiny sets things up, they are predetermined. It doesn't matter that Neji is a genius, he is of the branch family so his destiny is to serve and die for the Main Family.
For the Kyuubi...?
Obito knew that the seal for the Kyuubi would be weakest during childbirth, presumably from Zetsu or Madara. Kakashi mentions this at Rin or Obito's grave (Obito overhears) and attacks when he has the best chance to take the Kyuubi. Using the Kyuubi on Konoha was a mix of pragmatism and Obito lashing out.