This all reminds me of some folks I knew...
A married couple, man and woman. They didn't really get on well. He cheated on her, and refused to stop. They decided she'd see other people on the side, rather than divorce.
Eventually, his spur with extramarital relationships ended, and hers flourished. She met a woman that just wouldn't go home(the 'extra' relationships were supposed to be sexual in nature only). Eventually, they decided to 'marry' this other woman. After awhile, the two women got sick of the guy and kicked him aside, and the relationship became monogamous again.