I would say it goes hand in hand with family of origin issues. We feel profoundly attracted to, connected to, and comfortable with what is most familiar. Although it's not 100%, probably the majority of codependents are also ACOA's.
Harville Hendrix has a few books on the subject. The one I read was "Getting the Love You Want." He theorizes that we feel the most profound connections with those who possess the same traits as our primary caregivers when we were children--both the good and the bad. And that those relationships are the psyche's way of trying to "right the wrongs" of our childhood. Very interesting stuff.
L