Kindness can absolutely be cultivated. Mindfulness and Metta meditation can help, but also just doing to work on yourself.
I also would like to urge you to think of kindness as a quality of actions, not people. It’s what we do that matters more than our intentions.
ETA: kindness isn’t always seen as nice. A parent letting their kid suffer the consequences of their actions can be seen by the kid as unkind, but if it helps the kid become more resilient it has kindness.