Pretty much the entire 'Support Character' system had problems. Partially that Nintendo cut back the amount of script they needed to write by having nearly half the cast, beyond the Legacy Character DLC, not able to get Support Conversations with more than a handful of characters, and the Legacy Characters pretty much only have dialogue when fought against.
If they'd made time to actually make the Support System at least A-rank any normally recruitable character with any other, that would be fine, but for characters like Nowi or her child to have a Support Conversation option with Tiki... [sighs]