Extremes meet
Unity of opposites is described not in the philosophy only. They say that in a relationship extremes meet too. I guess it is one of the stereotypes declared by characters incompatibility. If different people get along well, so, some explanation must exist. A model girl and a rowdy-dowdy is the most popular example of such relations. This story is widely known in the cinema and literature.
Actually, two totally different people are not able to build healthy and stable relationship. They have different values, morals, visions, upbringing at least which could prevent the even and successive family relations. In an every day life these people could face the most difficult and unusual problems. It could happen that a rich wife would like to keep posh kind of life, but her husband earns for buying an apartment. But the parents of hers do not plan to help her as she did not want to listen to their protests against this misalliance.
As it is well-known, the hardest thing to do is to change a usual life style and character. But sometimes loves conquers all. And then it does not matter what your educational level is and how your spouse is educated. Sometimes you do not believe in something, but find it right next to you... or become a main character of the story.