This at best points to something being planned, not the Germa as we know them being planned. I could believe them being planned if a hint of Sanji's abuse or anything specific regarding them was mentioned anywhere in th first 800 chapters. And you don't know an overlooked detail has any significance until it's brought up. Can Nami's super-sensitiveness to weather be more than just talent? Maybe Usopp's knowledge of pirate lore and piracy in general has something to do with his supposed caretaker being a pirate? It's not like there are no theories concerning them in the fandom.
One more example. Sanji's name could be seen as a subtle hint to him being third son, yet we know Oda only used it because he couldn't use Naruto. Without this detail it could totally be used as a foreshadowing in discussion like ours. That things fall in one place doesn't mean they were always supposed to.
Anyway, w probably won't know unless Oda specifically confirms one way or another (maybe when Logs reach Zou/WCI?). But with how sloppy their inclusion in the manga feels (at least for me) and in the light of the recent knowledge of just how many things in OP were improvised, I find it more likely that nothing specific about Germa existed at the time the supposed "foreshadowings" happened.
Don't forget Sanji's reaction to Duval's mask, that's a clear reaction to his abuse.
Or him saying to Kuma that he'd be the one to cause the governament the most trouble, since he is the son of a WG family, albeit a disgraced one.
And, I'm not sure on this one, but I think some SBS or Databook revealed that Sanji was from the North Blue before we got to Jaya. But again I'm not sure if I'm recalling things correctly. But the fact that he came from the North Blue and had never been in the Grand Line was pretty significant since it meant someother way, that was never presented until now, to cross the Red Line.
The thing with his name could also have been what made some of his backstory. Naruto is/would be a reference to the spiral on his eyebrow while Sanji is a reference to the hours on a clock, iirc, it's possible that since Oda had to come up with a new name he ended up thinking more about the character too and made him the third sibiling of a family with that naming pattern.
There are plenty of things that were possibly improvised, like the Germa being a power rangers parody, the fact that they all share those eyebrows, that Judge was a parter to Vegapunk, etc, but Sanji being from a royal family seems to have been planned for the better part of the series even if that wasn't the plan the first time he appeared.
And since you mentioned the other characters' backstories Imma trow my two cents on them.
Nami is just a random girl. Franky's dad was just a bad parent to show how pirates are not always "good guys".
Usopp lived alone, he had his family's house to live in and the village seemed to take care of him as a whole. I mean, he was 17 when he appeared, why would he still not be living with that particular guardian at that age?
Zoro had/has a normal family on his native island. He has a last name, unlike most Straw Hat orphans, and no one mentioned him being orphan or homeless in his flashback. He just went to the dojo one day and that's the exciting part of his story.
Robin's father just wasn't needed for the story so he never appeared (as you see this applies to most of these entries, actually). My head canon is that Olivia was a single mother, maybe she once met someone on her travels and came home preagnent.
As for Brook, I'm in the camp that believes him being a soldier before he became a pirate is actually a plot thread. It seems that being a cop and then turning pirate is a running mottif in OP but it always has some explanation eventually. Lafitte also used to be a cop until he was expelled for being too violent, Brook doesn't share that trait so it must have been something else. Plus, he's old it will probably relate to some old story of how the WG worked back then.