It’s definitely iffy to have spouses serve on the same board since it gives a single household more power when it comes to community rules and resolutions. I’m no expert on the law, though, so I’d consult a lawyer if I were you.
If your bylaws don’t allow it, you can call the board’s attention and maybe recall one of them. A similar incident happened in our HOA but with committees. We had to remove one of the spouses from the fining committee because our bylaws don’t allow it.