I'm not married but I have seen my partner being fucked doggy by someone else a few times. Granted I was busy fucking someone else as well, so quite distracted, I'd still say her ass is pretty unique.
Now if someone put in effort to find some chicks with similar butts, I'm not sure.
Not too much to write. There is a couple we are friends with and sometimes we fuck while they visit and they watch or fuck too. Then eventually we swapped a few tims during that.