It is possible for a husband and wife to have one MP account (indeed, any two or more people can), so long as they have the same name. For example, Shannon Smith. Now, as ingenious as that is—and everything I say is ingenious by definition—it can be problematic if your spouse is of the opposite sex and you have "Mr" or "Ms" in your profile. And so too for international travel because you'd have different passports. But if you sanitize your profile of gender and remember to change your passport number as required, a conveniently-named, reasonably nefarious person could share an account with another homonymous cohort or two.

RNE, cautioning, "Not that I condone this subterfuge, mind you."