Elder son - Younger son
Madara - Hashirama
Sasuke - Naruto
I'll quote myself because you obviously can't read. Naruto VS Sasuke have been the main point of the manga
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Sasuke's hatred is worse than ever, he is relaxed because he now knows the truth abut Itachi and what happened that night. He also said ''I will go to that place, in order to kill you (naruto)
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Also, Sasuke is the new elder son of Rikudou. Elder son - Madara/Obito - Sasuke
Yunger son - Hashirama - Naruto
Tell me, what would be the point of Naruto VS Sasuke if they teamed up? Sasuke doesn't care about Naruto, and he wants to kill him with his full power. Now that he knows about Naruto's new power he will also seek power and not only knowledge.
Use your brain a little, seriously...