I believe that in relationship both parties need to devote to eliminating (bringing closer) the differences.

By bringing/moving closer we also learn new things and slowly make tighter bonds. Relationships that start ‘wider apart’ can make stronger bonds by bringing those differences closer.

One could say it’s that familiar pattern reappearing: ‘No pain no gain!’

‘Favorable Immediate Consequence Turn to Fatal Ultimate Ones’

If their differences are far apart, that represents the chance for (much) stroger bonds. But not anyone is capable of overcoming such differences.

I know some situations do not seem to fit into this ‘idea.’ But theoretically, if you could solve their issues it would create ‘unbreakable’ bonds. But both parties need to identify the energy and desire to work towards resolving.