Why are couples who are together so different?

We often wonder why that pretty girl married that dark-skinned man, or why that thin, handsome young man married that woman who has almost no favorable attributes, or why couples who are close are so different and often get divorced.

What happens is that couples first unite spiritually in space before incarnating (being born) and generally constitute themselves as companions of destiny, that is, as companions of struggle those who have greater material affinity, which means that they have greater situations in common, as common debts both of justice and of lives among others; so why the companions of destiny have been before, in other existences parents, brothers, cousins among others, is, therefore, greater affinity one of the other.