SDF Macross is a great show, but it has a lot of issues. A lot of these tie into the characters, the main cast in particular are pretty bland (Do You Remember Love did a lot to fix this). However, Macross has always done a good job of fleshing out the supporting cast, regularly including random semingly unimportant scenes of minor characters just hanging out. Which goes a long way towards making them feel like real people with lives outside of their interactions with the main characters. Max and Millia stand as a shining example of this.
Ace pilots on opposing sides of the Zentradi, Human conflict, their first combat encounter leaves the previously undefeated Milia fuming, so she has herself micloned and infiltrates the Macross, intending to face her opponent in single combat.
They have an intsense virtual dogfight, then a high quality knife fight, and then they get married. Within 2 episodes.
This whole scenario is inherently absurd, but it works somehow. The couple go on to become a key part of the eventual peace between the Humans and Zentradi, but more importantly, they have lives. They have children, and become the best parents ever.
At one point they take over a space station using their baby daughter as a weapon. Best parents ever.
Flashing forward to Macross 7, they’ve become a rarity within the franchise, recurring characters. Having become the Captain and Mayor respectively of the Macross 7 fleet Max and Millia have ultimately drifted appart. Shocking as this is given that their marriage was based on the firmest of foundations – trying to knife one another in the park (as both of my parents are from Glasgow I find this highly plausible and realistic) – it again contributes to the sense of the Macross universe as a real place where people exist independant of the plot. Sure, it might not be the happy ending one might hope for but, sometimes life is rough, people who were once deeply in love drift apart. It’s heavily implied that they become closer again towards the end of the series, and they clearly still care about each other, with the stresses of their respecitve and often conflicting jobs being the main sticking point keeping the pair estranged.
Ultimately it’s never outright stated how they end up, although their descendants continue to crop up and play various roles throughout the franchise, which works in their favour. They have their own lives to live, off screen.