You could play with that though since "both sexes" could be perceived as "both individuals that have a sex" and "husband and wife" don't have any technical meaning.
It's already a play on 両姓(both surnames), which could have meant that parents could constitutionally block marriages. Not that it matters, though. People are frankly more concerned about tax frauds and crime record laundering abusing same-sex marriages than imagined traditional family values.
I'm not a lawyer, but they're working on it.