Dan Cere wrote a fine essay on how the "close relations" theory is quickly displacing the conjugal theory of marriage in the laws of this country and Canada. I have written about it before. For their final examination, my family life students had to consider all we had studied in light of this conflict of paradigms. I learned something, as I always do, from these examinations.
One of the ideas we spent some time with is the Beavers Scale of Family Functioning, a family systems account that divides families into five large categories of functioning from chaotic to optimal. One of the points that Robert Beavers emphasizes (as does the author who popularized his view, Maggie Scarf) is that well-functioning families have clear boundaries around their various roles. The boundaries should not been too rigid, but neither should they be too permeable. But in order to have boundaries around family roles, you need to have some dependable roles to begin with. Beavers builds on the boundaries around the marriage, around the parent-child groups, and around the family as a whole, in addition to subsidiary roles.
The conjugal theory is, obviously, built around the roles of husband and wife. In the more amorphous world in which any close relationship is as good as any other, and none are assumed to be permanent, "family roles" melt away. In fact, under a close relations model, I don't see how we could talk about functional and dysfunctional families at all. This may be part of the appeal of the close relations paradigm to postmodernist intellectuals. The freedom from defined roles is likely to be cold comfort, though, to children caught in the chaos of a formless family.