Dialogue is a powerful tool, but it’s very rare that anyone—even characters—will come out and say exactly what they think or feel at any given moment. Instead, body language and action can help convey these things.
As an exercise: Take a moment and write a slice-of-life flash fiction, showing how your characters interact with each other. What are some of the little, daily ways they show they care about each other? How might their innocuous habits be used to show dislike of each other? Which of these things are done deliberately, and which do your characters do without consciously thinking about it?