Naruto linked to Hashimaru was possiblities by descendant.
Senju Hashimaru married Uzumaki Mito, the close relationship between 2 clans.
Kushina was from Uzumaki clan. The missing link was Senju to Namikaze Minato. From here, Minato + Kushina = Naruto (both by descendant)
This linked could be most probably as what Madara said about Nagato Uzumaki. That's why Madara wanted Nagato to bring him back as normal life, instead by Kabuto thru Edo. By giving Nagato the special Rinnegan, he became the "mini version" of SO6P. Like what Nagato did to Leaf Village - the sphere (moon by SO6P) and restored the "just killed by him" back to Normal Life.
The unknown linked of Namikaze Minato from Senju. The other unknown link of Uzumaki clan may not be from SO6P but could be from one of the sibling of SO6P (if there is).
Bijuu. Hashimaru had chosen Kyuubi and the rest to other countries. Hashi then insert kyuubi to his wife, Uzumaki Mito. Next to Uzumaki Kushina. Minato was said to be genius of his generation, but may also be from Senju.
Hashi could knew there were certain power of Kyuubi and so do Minato. SO6P separated the Ten-Tails chakra into 9 parts (SO6P had the abilities to create things from nothing), Kuubi being the last having the 9 tails. Possibility was Kyuubi being the last, will had the remaining chakra of the Ten-tails. As 9 tails could sense "Evil".
Example: If you are making cup of Tea/Coffee drink. First you put the milk into the cup. Then pour the tea into the cup. If you do not stir, the milk remain at the bottom.
No kakashi did not know tajuu kagebunshin, just kagebunshin
During Naruto training by Kakashi, Kakashi said only Naruto chakra could be hundred-fold (Ch.315). Naruto, during earlier days, he had taken the forbidden scroll and able to master the kage-bunshin, in such short time. Naruto had 2 powers -(1) Kurama; and (2) Hashi descendant (body & strength). That's why Minato knew Naruto would be strong with Kurama power inside him.
Ok maybe instead of uzumaki seal being the source, rather it originates with Kurama (so6p, hashi, mito, minato, kushina)
I mean I know this might all sound silly but Hashi and Naruto seem linked more than just "will" but thats just me
No. not person.