meh
Bro compare the grandchildren of both the Senju brothers
Hashirama => Tsunade
Tobirama => Minato (as predicted by you)
Tsunade's age and Minato's age should be more less within a close range. There's no match for their ages. Jiraiya seemed to be an old man facing Minato.
On the base, members had even made theories on Minato being the son of Jiraiya and Tsunade (hidden s*x)
tsunade is the eldest granddaughter
nawaki looked a lot younger than her,
if tobirama had 4 childs (just like his father(assumption))
15 year of age gap is not even a big deal