Alright, give me a few minutes and I will edit this post with my build recommendations.
First pair: Kjelle and Owain. Unfortunatally because of the lack of Galeforce on Owain the most optimal build is ruled out, with both using galeforce to allow both to attack at least once and ensure Tank!Kjelle is the one in front for the end turn. However, there are two options avaible.
Option 1: Kjelle: Sol, Aeigs, Pavise, Vantage, Galeforce
Owain: Athema, Swordfaire, Agressor (DLC), +10 Resistance (DLC), Allstats + or Limit Break (DLC
Option 2: Kjelle: Luna, Galeforce, Dual Guard+, Dual Support+, Astra
Owain: Vantage, Vengeance, Wrath, Athema, Tomefaire
In option 1 you have Kjelle always lead. In option 2 you have Kjelle attack first, trigger galeforce, then switch to Owain for the second attack
I will get the other 3 pairs when i get out of class.
Pair 2: Noire and Inigo
Alright, Noire is able to be built as an Sorcerer Tank. Give her nosferatu and you're good. Inigo will be pure support
Noire: athemena, Pavise, tomebreaker, hit +20, renewal
Inigo: afmthrift, tomefaire, deliverer, dreadfighter stuff. Go either Sage or Dreadfighter on this one.
Pair 3: Severa and Yarne
Alright, the plan for this one is offensive Severa, tank Yanre. Attack first with Severa, get galeforce, switch Yarne on second attack.
Severa: Luna, Dual Guard +, Armthrift, Galeforce, Athema. Class should be hero
Yarne: Pavise, Aegis, Deliverer, Axfaire, Luna
Pair 4: Gerome and Nah. Okay, this is a hard one honestly. They both have fairly decent builds you can make out of them, but neither are particulary complementary. Lack of galeforce rules out making one tankier and the other more offensive, while neither have enough support abilities to really work one into a lead and another into an support. So I'll just give builds for each that ignores that the other is even there.
Gerome: Vantage, Sol, Astra, Swordbreaker, Counter
Nah: Luna, Aegis, Bowbreaker, Swordbreaker, Lancebreaker.
Alternativly, you can go super questionable support Nah from with. Dual Guard +, Deliverer, Bond (DLC), Limit Break(DLC) and Bowfair. Make her an Sniper to take advantage of bowfaire
Pairless: Brady. Healbot. Go with War Cleric for the added tankyness. Luna, Aeigs, Renewal, Vantage, Miracle. Basically run around healing and supporting with staves, and hope tank stuff keeps him from dying.
PS: Replace Relief on Cynthia with Pavise.. While she;ll only be lead for one attack per turn, it will still mean she is taking less dmg.
Note: In most cases I could make better builds for each character if I am taking them as an individual. However, I am instead looking at their pairs and trying to make builds that complement one another, which should add up to a whole greater than the sum of their parts.