I do feel like I have always in my life been inclined to be on the outside walk a different path or something. Because of that and increasingly over the years my sense of distance from mainstream society or from the way culture works I have a different kind of perception of it.
Straight couples don't have to be monogamous to be married or married to be monogamous. Monogamy no more defines marriage than the presence of children does. Monogamy isn't compulsory and its absence doesn't invalidate a marriage.