When you visit you might like to encourage them to have some "alone time" together, any opportunity to talk privately, perhaps even a couple of hours. When my brother or I visited our parents with our partners, I/we made it a point do something with our Dad -- e.g. go to the pub with him, or play a game of squash -- while our partners did something else, for example go the cinema with Mum, help in the garden, workor do some homework alone on their computer, or anything like that.