She is a perfect example of what being hero is about: being in constant danger, your family being in constant danger cause villains want retaliation. Bad parenting aside, recently, Natsuo Todoroki was targeted as well, by a villain that wanted to reach Endeavor, that's a constant risk as a hero. There's no time to play family when you have to save the world. This is what I meant, they have no means to be good parents, not that they are bad, it's just hard.
Alright, then. I misinterpreted your intentions when you said "terrible family guys".
Is there a risk to it? Yes, that much is fair, not only in BnHA, in any fiction any superhero's family could potentially end up dead in the fridge like Kyle Rayner's girlfriend, but isn't Deku's class filled with people who have happy heroic or non-heroic families that do just fine in that regard? Like Ingenium's.
For that to be a strong point in this particular matchup, the necessary question is this one: Does being Seiya's wife/husband not entail the same potential risk of being targetted by his enemies?
If it's about having time to play family, Mirio has shown to be pretty good at having enough time to take good care of Eri while he's still a student, which also reminds me of another one of his good points: The fact that he took such good care of her after losing all that he had worked so hard for for the past three years, shows just how positive and caring he is. Yes, he's mostly a hero but, in his case, most of the qualities that made him a good hero also made him a good potential husband.