I know how you feel.
Here's what I do. I put my 90 minute drive to see family to good use by visualizing the visit in a positive way. I see them saying what they always say and then myself responding calmly or switching the topic to something pleasant.
Think of yourself as having numerous strands of connection to your family, some positive and some negative. Your task is to let the negative strands wither and die while nourishing the positive ones.
For example, a hypochondriac relative starts complaining about their health:
Hypochondriac: My heart palpitations have me worried.
You: It's a good thing you have such a great doctor. You are in the best of hands and look fine to me. Indeed you are the picture of health for a person of your age. (A true statement.)
If things get really negative, I'll change the topic with a question like "So tell me about something good that's happened in your life lately."
I have some relatives who have been dumping their imagined ailments on me ever since I can remember. Changing the topic quickly is one way of reducing the topic's frequency over time. You are actually doing them a favor by making them focus on positive topics.
One final tip: limit your visits to a tolerable duration and don't hesitate to leave early if they are really starting to depress you.