Siegbert
Parent Xander
Default Class: Cavalier
Recruited on: Paralogue 15: Hidden Bravery
Possible Mothers/Fathers: Azura, Beruka, Charlotte, Effie, Felicia, Hinoka, Mozu, Nyx, Peri, Sakura, Selena
One of the best choices is Effie as she gives STR boost and this also gives Siegbert access to the Knight/General class where the skill Pavise (Halves damage from Sword, Lance, Axe, Beaststone, Faceless, and Puppet attacks) is acquired. With Siegbert promoted to a Paladin, he'll have access to another defensive skill Aegis. (Halves damage from Bow, Magic, Hidden Weapon, Dragonstone, Breath, and Boulders) With these two on, you'll have a sturdy mounted unit that can deal solid damage and capable of tanking any enemy attack. In the other hand, Charlotte can also provide STR boost and give more class options.
Forrest
Parent Leo
Default Class: Troubadour
Recruited on: Paralogue 16: Abducted
Possible Mothers/Fathers: Azura, Beruka, Charlotte, Effie, Felicia, Hinoka, Mozu, Nyx, Peri, Sakura Selena
The gentle Forrest is not meant for melee Combat so if you want him to be more effective in battle, you may want him to continue to advance line in becoming a Strategist. Nyx seems to be a good option since she gives Forrest MAG and RES boosts. Sakura is also a good option since gives Forrest access to another healing class to complement his default staff proficiency.
http://resource.supercheats.com/library/2016/1460244528ignis_portrait.jpg
Ignatius
Parent Benny
Default Class: Knight
Recruited on: Paralogue 17: Two Defenders
Possible Mothers/Fathers: Azura, Beruka, Camilla, Charlotte, Effie, Elise, Felicia, Mozu, Nyx, Oboro, Peri, Rinkah, Selena
Effie or Charlotte can boost his STR and even further improve his already high DEF through Effie won't be able to provide a new class option for Ignatius. Charlotte gives him access to either Berserker or Hero class sets. Peri offsets Ignatius' low RES by giving him a boost to that stat. Beruka and Camilla both give him access to Malig Knight skills like Savage Blow and Trample, both complements his frequent need to take on multiple enemies and staying in the front lines. His unique skill, Guarded Bravery gives him two effects whenever he's supported or not.
Velouria
Parent Keaton
Default Class: Knight
Recruited on: Paralogue 18: Nutty Family
Possible Mothers/Fathers: Azura, Beruka, Camilla, Charlotte, Effie, Elise, Felicia, Hana, Mozu, Nyx, Peri, Rinkah, Selena
Velouria's unique skill, Good Basket allows her to recover 10HP (fixed) by LCK% trigger. Beruka and Camilla both give him access to Malig Knight skills like Savage Blow and Trample as well as good DEF boosts. Charlotte or Rinkah gives Velouria access to other class sets and skills though their stat boosts are geared towards STR which can turn Velouria into powerful but vulnerable attacker.
Percy
Parent Arthur
Default Class: Wyvern Rider
Recruited on: Paralogue 19: Great Heroism
Possible Mothers/Fathers: Azura, Beruka, Camilla, Charlotte, Effie, Elise, Felicia, Kagero, Mozu, Nyx, Peri, Selena, Setsuna
Percy will have access to great Malig Knight skills should he be changed to that class (Savage Blow and Trample). His unique skill, Fortunate Son, boosts his Ddg by 5 and all allies within two spaces by 15. Camilla and Beruka further enhances Percy's stats fit for his default class but won't provide much of re-class options. Effie provides good STR and DEF boosts to him while giving access to a good defensive skill (Pavise). Like Effie, Peri also gives Percy access to another good Paladin skill (Aegis).
Ophelia
Parent Odin
Default Class: Dark Mage
Recruited on: Paralogue 20: Ultimate Power
Possible Mothers/Fathers: Azura, Beruka, Camilla, Charlotte, Effie, Elise, Felicia, Kagero, Mozu, Nyx, Orochi, Peri, Selena
Fortunately, Ophelia didn't inherit his father's annoying unique skill. Her unique skill, Bibliophile increases her Crit rate by 10 when she's carrying 3 or more tomes/scrolls. Nyx, Orochi, and Elise gives her great MAG boosts. Nyx further increases her MAG damage output while Elise and Orochi gives her more re-class options, capable of dealing fearsome magic damage while having access to staves/rods at the same time.
Soleil
Parent Laslow
Default Class: Mercenary
Recruited on: Paralogue 21: Bright Smile
Possible Mothers/Fathers: Azura, Beruka, Camilla, Charlotte, Effie, Elise, Felicia, Hana, Mozu, Nyx, Orochi, Peri, Selena
Soleil's unique skill is Sisterhood which allows her to deal +2 damage and take -2 damage when supported by a female ally. Camilla and Beruka further enhances Percy's stats fit for his default class but won't provide much of re-class options. Effie provides good STR and DEF boosts to him while giving access to a good defensive skill (Pavise). Like Effie, Peri also gives Percy access to another good Paladin skill (Aegis). Camilla and Beruka gives her access to great Malig Knight offensive skills should she be changed to that class (Savage Blow and Trample).
Nina
Parent Niles
Default Class: Outlaw
Recruited on: Paralogue 22: Abrupt Clash
Possible Mothers/Fathers: Azura, Beruka, Camilla, Charlotte, Effie, Elise, Felicia, Mozu, Nyx, Oboro, Peri, Selena, Setsuna
Nina is a potentially strong character, depending on the mother you'll choose for her. Her unique skill, Daydream, has an oddly specific requirement to trigger. She must be adjacent to two male characters paired together. Charlotte and Selena both gives her access to the Hero class which also gives the very useful Sol skill. While Charlotte does give good STR boost, Selena opens up the Bow Knight re-class option, which gives her access to the Bow Knight class while preserving her good bow proficiency. Camilla and Beruka gives her access to great Malig Knight offensive skills should she be changed to that class (Savage Blow and Trample). Effie provides good STR and DEF boosts to him while giving access to a good defensive skill (Pavise). Like Effie, Peri also gives Percy access to another good Paladin skill (Aegis).