What Krishna says about marriage?

Bhagavad Gita talks about a relationship in two terms - horizontal and vertical. True vertical relationship is with Krishna and the only eternal bliss that we must attempt to achieve. We as eternal souls must attempt to have a relationship with the eternal Krishna.
Then at the horizontal level, we must attempt to have relationships with those who share our familial status. These include the relationship between elders, younger ones or siblings. While it is important to sustain horizontal relationships, we must also attempt to boost the relationship with Krishna. The best idea is to harmonize the horizontal and the vertical relationship and seek Vedic wisdom and culture to promote a compatible social structure.