I was watching some Shippuden when I started realizing that Jiraiya and Sakumo have quite a few similarities. My curious side took over and I started researching and here's the notes I took. Sorry if it's all over the place, I was super hyped that I might've just found out if Jiraiya really was Sakumo.
Is Jiraiya the White Fang?
-Kakashi aged 13 during his Gaiden
-Father killed him self within 1 year 5 years prior to Kakashi's Gaiden
-Kakashi is aged 7-9 during fathers' death [Edit- Sakumo died 5 years before Kakashi became
a Jonin, and being the youngest Jonin ever at age 10, Sakumo died when kakashi was 5]
-Lots of people are saying that Sakumo was the same age as the Sannin, or that he was
24 when Kakashi was born, meaning that if Sakumo died whithin a year 5 years before
Kakashi's Gaiden(he was 13 at the time), he would've died at age 32(24+8=32), which is
an age a lot of people thought the Sannin were at their prime at the point of time Sakumo died. And
since Kakashi is 22 years younger than Jiraiya, that means if Sakumo didn't die, he
would be 54 years old, which is Jiraiya's current age. (Since the timelines are a bit messed up, just take whatever age you find Sakumo to give birth to Kakashi to, add whatever age you Kakashi to be at when Sakumo dies, and then add the age difference between Kakashi and Jiraiya.) Sakumo and Jiraiya also share
many similar traits. And many many people suggest that Sakumo was at the same skill
level as the Legendary Sannin, so in the end, it is extremely possible that Jiraiya
is the White Fang of the Leaf.
-Sakumo raised Kakashi in a way that made him one of the strongest Shinobi in the world
of Naruto. Lots of people also suggest that Sakumo and Minato are very similar as well. And
since Naruto was still an infant when his father died, his father couldn't of trained him.
If Jiraiya is Sakumo, then it makes sense, because Sakumo raised Kakashi to be one of the
strongest shinobi in Naruto, and Jiraiya trained Naruto to become one of the strongest
ninja as well.
Feel free to discuss on this because honestly I was just all over the place due to the fact I was tired and hype as hell.
[Quick Edit]-There's a few things in here I meant to delete but I guess this shows all of my thoughts since its 100% raw notes.
It's a solid theory, which you debunked in your own notes. Sakumo was said to be on par with the The Legendary Sannin, yes, and the Legendary Sannin were Jiraiya, Tsunade and Orochimaru. So if he operated at the same time as them and his prowess was repeatedly compared to the Sannin then there's no way he could be Jiraiya since Jiraiya was one of the Sannin. I butchered my point, but I hope it got across to you.
There's also the fact that Kakashi met Sakumo in Purgatory (that's the name I'm giving to that place) when he got killed by Deva Path and he definitely was not Jiraiya, as evidenced by the lack of tits-related metaphors in their brief conversation.
Still a solid theory though, especially if we consider how similar Sakumo's and Jiraiya's hair-do were in that Purgatory sequence and Jiraiya's and Kakashi's obsession with erotic novels.
On a side-note, it's real shit that we didn't get at the very least a filler episode about Sakumo. He seemed like a cool character.