“Only with an understanding of complementarity in marriage do we have any grounding for monogamy and exclusivity [in marriage; thus, fidelity].”
[By complementarity he means roles that are hierarchical and patriarchal.]
So, according to DeYoung fidelity is determined by role not by love; he has here accused all egalitarians of not having a grounding for a faithful monogamous marriage.
[SMcK: According to my sources, Kevin DeYoung means by “complementarity” only male-female marital relations and not the typical use of complementarianism. In which case I still find his “any grounding” to be an overstatement since it takes away the “rugged commitment” dimension of “covenant” in a marital relation. Yes, procreation does create the situation for more stability in a marital relation, but “any grounding for monogamy or exclusivity” is an overstatement.]