That sucks. However, even rare coincidences happen all the time. There are about 8 billion people on the planet, and all of them have two parents that could die

That sucks. However, even rare coincidences happen all the time. There are about 8 billion people on the planet, and all of them have two parents that could die of cancer. It won't be common for them both to die of cancer, and even rarer for them to die of the same type of cancer, but if you multiply any small number by 8 billion you’re going to get a rather larger number. You probably don’t have any more or less radon exposure than the average person, so that risk factor won’t be any higher for you than for anyone else. Given your genetic risk factor, it might be worth paying more attention to radon than average, but probably not worth stressing over it. Install a radon monitor and pay to have it regularly tested and maintained, but don’t let worry run your life. It might be a good excuse to move away from the mountains and go live on the beach though. :)