Okay, so I’ve got this One Piece theory going and it’s about Brook being pretty sus (no, not in that way).
that ‘leader of a battle convoy in a certain kingdom’ is something that is still waiting to come into play.
And that ‘certain kingdom/island’ is what Oda always uses when he doesn’t want to reveal an island name yet.
That’s the base line, but then:
Brook knows the Vinsmoke family name very well, to the point of terror, despite the fact that he’s from the West Blue and they’re only active in the North Blue and exist only as myth in the other blues (Nami says as much for the East Blue, but I didn’t feel like grabbing that panel).
Robin’s also from the West Blue and she has a reaction that’s more expectable. She only vaguely knows the name (and she could’ve easily heard it from Crocodile or the Revolutionary Army after leaving the WB) and doesn’t have the same visceral reaction Brook does.
And, while Chopper and Nami have pretty good reasons to join the stealth (HA!) mission to save Sanji - Pekoms would die from his injuries with Chopper and Luffy couldn’t navigate his way out of a community pool without Nami), Brook’s reason of ‘I feel really bad about Sanji being taken while I was around’ is a bit thinner on the ground.
Anyway, something, something, Brook is hiding something. Something involving the reasons why he left a position as a battle convoy leader in his home kingdom (which I suspect is a high position, close to the royal family) to turn pirate and Sanji’s family - grandparent, most likely.
Occam’s razor suggests Germa making a rare trip to a merc job in the WB, like what brought Sanji to the EB, and attacked Brook’s home kingdom, leaving Brook broken, having failed to protect his home and unable to die because of his power.
But, narratively speaking, I don’t expect it to be that shallow. A bases, yes, but as a start for some deeper connection between Brook and Sanji.
This is brings me out of speculating by connecting existing threads to assuming details wholesale, but it could involve Sanji’s mother, Sora. Assuming she was around the same age as Judge at the time of their marriage - and that she wasn’t entirely consenting in it - the timeline fits that she would’ve been a young child at the same as when Brook turned pirate.
And I can easily see the evil scientist rulers of Germa 66 being down for a little light child abduction for human experimentation fodder, especially going into Judge’s superhuman experimenting that he turned onto his own children.
I’m going to keep my hard theory to just ‘Germa attacked Brook’s kingdom’, but my soft theory is that Sora was someone Brook knew personally, either a member of the royal family he was sworn to protect or even his own family and she was taken by Germa as a child.
Edit: Perhaps this is long too late an addition to expect people to see it, but I’m including this expansion:
(Behold my lazy attempt at omitting an unneeded panel.)
We have a moment where the crew starts speculating on Sanji’s family and what that moment ends on is a quiet non-reaction from Brook. That is certainly an odd choice when you think about it.
