Re: Minato > tobirama
Agreed on that. Hairstyle tends to follow gene pool in this manga. Also, it is a coincidence that Dad and Son just happen to master those particular jutsu invented by Tobirama.
1. Regarding the techniques, it's a stretch, many people have the same jutsu (Deidara, Itachi, Hiruzen, Konohamaru, Orochimaru, Jaraiya, and even KIBA have done shadow clones..) ... it's not that rare).
2 Going by the hairstyle trends, Kakashi and his father are probably Senju as well on Tobirama's side.
3. The real mystery is the link between Hashirama and Tsunade - There's a Senju/Uzumaki (Hashi married an Uzumaki) in there that's never been mentioned, and Tsunade hasn't ever revealed her last name. This person is quite likely the parent, or grandparent of Minato. (making Tsunade Naruto's great-aunt)
4. There's no logical way that Minato is Tobirama's son - first off, when the Kage were reincarnated by Orochimaru.. he was like, "Who the hell is this guy?" to Minato. Given that Tsunade is Tobirama's GRANDNIECE (Hashi's granddaughter), the timeline wouldn't make any sense at all, considering that Jaraiya (the same age as Tsunade) was Minato's MENTOR. There's nearly 4 generations of shinobi in age between them. Minato has a better chance of being Tsunade and Jaraiya's lovechild, than Tobirama's kid.