Our Gemara on Amud Aleph discusses the matter of a couple who is childless for ten years.  Since the husband is obligated to fulfill the mitzvah of Periyah Ureviyah, he would have to divorce and marry another woman.  Yet, since we are unsure whether he or she is the cause of the infertility, she still gets her kesubah, and she may remarry as well to try again.  The rationale is: 

שֶׁמָּא לֹא זָכָה לְהִבָּנוֹת מִמֶּנָּה.

it is possible that they are not a suitable match for bearing children.

In other words, their inability to have children might not be as a result of either person’s infertility alone, but rather a combination of the two (see Arukh Hashulkhan EH 154:28). It is kind of like when two recessive genes are a poor match, but if only one spouse has a recessive gene, it is not a problem at all.  The Gemara may mean this in a spiritual sense as well, the combination of husband and wife did not bring out the best in each other, and thus they did not merit having children. 

Elsewhere we have noted that spiritual, emotional and physical patterns often repeat throughout the material and spiritual world (see Psychology of the Daf, Yevamos 58).  I wonder if this idea of incompatibility in the combination, as opposed to it being one person’s fault can also be applied to marriage success or failure, overall.  Perhaps it is fair to say that sometimes a couple finds it necessary to divorce not because one spouse or the other is particularly defective.  Rather, as a combination of qualities, they did not merit to be productive as a couple.