Alright, rather than telling you who to put with who for the last 4 pairings, I will instead say who is good for each kid.
Gerome
- Vaike: +7 strength mod but otherwise poor stats. Luckily he will be going support mode for Cynthia in this case, you just stack things to increase his damage outpit. Axfaire, Aggressor, Dual Support + (inherited from his mom), All Stats +2/Resitiance + 10, and Limit Break
- Gaius: Decent enough tank mode. Sol, Vantage, Deliverer, Counter/Swordbreaker/Lancebreaker, Reniewal
- Ricken: Same as Gaius, only replace Vantage with Aegis
- Kellam: Can be built as either support or as tank. For Tank replace Vantage/Aegis with Pavise. For support you go Dual Guard +, Dual Support +, Agressor, Allstats +2/Resitance +10, Limit Break
- Virion: While the pairing between him and Cherche is great storywise, gameplay wise this is awful.
- Libra: Gets Athema and Hex for support. Not bad either.
Yarne
- Vaike: +6 strength mod, but you already knew this. Support build, same of your third file
- Gaius: Fairly good tank Yarne. Sol, Vantage, Counter, Lancebreaker/Swordbreaker (inherited), and some filler.
- Ricken: Gets pretty good stands Dual Guard + on the support side of things. Also Luna and Aegis if he is going to lead
- Virion: Not great, though does give access to the Wyvern Rider tree (which panne gets, but Yarne doesn't normally. So while you can have him inherit stuff from it, this lets you get multiple things). This could work if he is paired with a galeforcer, but this is otherwise average.
- Libra: Gets renewal for a lead build and Athema/Hex for a support build, but otherwise is missing some tools. I would say this pairing is average
Brady (remember, he can either inherit Galeforce or Dual Support +)
- Vaike: Oddly leads to a pretty good offensive Brady. Galeforce, Luna, Axfaire, would be a must, with then a mix of support or defensive skills depending on if he is going to purely lead or galeforce support
- Gaius: Again, fairly good offensive here, getting stuff like counter, vantage, sol. Besides the stats not being good for it, he might actually be half decent tank
- Kellam: Gets Pavise and nothing else good. Though stats aren;y bad and can become decently survivable
- Ricken: Gets not much new, but gets a high magic. Since Brady already has good stuff for support, this would not be bad. For this run Tomefaire, Dual Support +, Dual Guard +, Agressor, Resistance +10/Limit Break
- Libra: As above, but with Athema for even better support.
- Virion: Not much here. I think there may be a trend with Virion not giving much good stuff. Though the wyvern tree might make him a half decent tankyish build in a pinch
Noire
- Vaike: Kinda bad, since Noire can already do the whole Sorcerer tank. While this does give her Sol, that is useless here since Nosferatu is a thing that exists. Armthrift can be useful so she can then run a forged Aversa's Night and having it last more than 5 seconds
- Gaius: Galeforce time! And broken sorcerer build thing. Awesome! Doesn't get Wrath though, so instead of a high crit tome go for an Celcia's Gale for multi attacks.
- Kellam: Reniewal and a good defense. Would help with tanking, but little else
- Ricken: +6 magic, with an additional +5 from Tomefaire? Only Morgan and Ricken!Laurent have this high magic (with Morgan mothered/fathered by either her or Laurent going higher). Also gets Aegis for tankingness should you go that route.
- Virion: Gets tomefaire... and not much else.
- Libra: Same deal as Gaius with 1 less magic and Reniewal instead of Aegis
Note: Everything i said about Gerome supporting Cynthia also applies to F!Morgan. Also, as much as I prefer Ingio with F!Morgan and Gerome with Cynthia, and that both those pairings will work, having those pairing switched would be slightly more optimal... though as I said, both options would be good.