Are married swinger really in love & happy?

I think that it would be difficult looking @ some1 you are in love with have sex with some1 else.I would like peoples thought on this.Is there really love in a marriage like that? Or just fun & lust? I think that 1 of the 2 would not love the other person or they just are married because they feel safer having sex with other people & having some1 you would trust in some way too?Or could it be that their relationship started as friends that would have sex & date other people 2? I'm just wondering is there & can it be any real love in a relationship & marriage like that?