Meditation is generally seen as a solitary pursuit, but the benefits can extend far beyond ourselves.
The effect that meditation can have on a relationship generally comes from focussing on improving the individuals within it, rather than focussing on the relationship as a whole. Often when we look at the faults in a relationship we detach them from ourselves and our own behavior, when that can be if not the core, then a contributing factor.
Gaining insight into our own behavioral patterns and understanding how we are acting is one of the enormous benefits that meditation has to offer. Science is evermore piling on the evidence in support of the idea that increased self-knowledge can help defeat self-destructive patterns, and thus preventing them from impacting relationships. 
Insights that lead us to empathy
But it is not just damage prevention that increased self-knowledge can provide – the more we understand about our needs, the better we can cater our relationships to fulfilling them. Whether its affection, responsibility, or direction, when we know what we need to feel fulfilled to be able to build a positive relationship around it,
Alongside our own needs, the more we understand about ourselves, the more we are able to empathise with others, especially our partners. This empathy helps us see what they might require in order to gain the fulfilment they need from the relationship too.