Lucina doesn't really need swordmaster. She doesn't need Astra. Aether is better. Vantage's usefulness is circumstantial. The one skill you miss out on that Lucina can use is Swordfaire which will easily be replaced when the limitbreaker dlc comes out. Until then, All Stats +2 is arguably just as good.
Chrom x Olivia is however an excellent choice for Inigo.
Recomendations:
Sumia: Chrom or Gaius
Chrom/Sumia will give Lucina access to Renewal, Pavise and Aegis. Makes Lucina a surprisingly effective tank. Cynthia will suffer a bit though.
Gaius will give Cyntia the sword master and assassin class which she can utilize, plus most of the defensive skills Sumia has access to.
Cordelia: Stahl or Lon'qu
Severa doesn't need much since her mother is already a boss. You just need someone to pass on myrmidon and she's set. Stahl has better physical mods while Lon'qu will make Severa's speed and skill skyrocket.
Sully: Donnel or Gaius
Sully doesn't pass on the pegasus knight class so you need a male character that does. Donnel gives Kjelle Mercenary and Pegasus Knight. Two great reclass options at the cost of some relatively poor stat mods. Gaius gives better mods but can only offer pegasus knight as the one note worthy reclass option.
Olivia: Chrom (but generally does well with anyone)
Olivia is rare in that she passes on all the important classes and galeforce all on her own. Chrom allows Inigo to inherit 'Rightful King' which can boost Armsthrift past the 50 Luck requirement for infinite legendary/forged weapon use and Astra/Lethality's proc rate. If you're not going for Chrom then you'll want someone who passes on good stat mods. Gregor, Stahl or Vaike are all good candidates.
Lissa: Henry, Libra
Owains mods make a good physical build difficult so it may be better to boost his superior magic mods. Both Henry and Libra allow access to the Dark Mage branch and thus the best mage class in the game. You'll want Lissa to pass on Galeforce.
Miriel: <s>Lissa's leftovers</s> err... I mean any Mage oriented character works. Lon'qu also isn't a bad choice if you want to give Laurent access to Vantage, Astra and Lethality. Though on the most part, there isn't much you can do to prevent Laurent from being a carbon copy of his mother.
Tharja: Donnel, Gaius, Ricken or Lon'qu
Like Sully, Tharja doesn't pass on the Pegasus Knight class. Besides the avatar, Donnel or Gaius is the only possible remedy to that problem. Ricken does't pass on Pegasus Knight but he does allow Noire to be a proper mage and learn Tomefaire. Also has the best magic mods among male characters.
Maribelle: Libra, Ricken. Possibly Donnel.
Brady's terrible physical mods make him nearly unsuited for anyone but a mage character to be his father. However a surprisingly high luck stat makes Donnel a strange but viable candidate for Armsthrift exploitation.
Cherche: Gregor or Vaike
Excellent physical mods regardless. Gregor gives access to myrmidon and mercenary. Vaike has slightly better mods but a worse reclass selection. Both are great fathers.
Panne: Any physical oriented character.
They're all viable.
Nowi: Donnel, Gaius, Kellam or Vaike
Depending on what you're looking for. Donnel and Gaius will pass on Pegasus Knight and Gale Force. Kellam makes Nah potentially the best tank in the game. Vaike has great physical mods and can pass on counter and the mercenary class for females.
