As in they are all under the younger so6p son family tree. All three clans seems to be linked to life. Hashirama had earth, water, and wood release and he was senju. The Uzumaki clan had longevity and vibrant hair. And Jugo's clan was able to use nature chakra naturally. It may also explain why Naruto could achieve a perfect sage mode if he was distantly related to Jugo. The younger son was had "yang qualities" like these other three clans ( the life force and physical energy.)
What do you think? :shrug:
What do you think? :shrug: