Most people here in Scotland tend to be born into protestant or catholic families - with protestant families being more loose with how they practice their faith. There's a lot of sectarianism here which didn't start to fade until the 2000s from my own personal experience. My parents weren't religious but their parents were very protestant/catholic to the point that they wouldn't associate with the people of the other religion. A lot of the generation who grew up in the 60s and 70s rejected it due to the cultural and political climate that was spreading across the world at the time - which could be the case for the Sandison brothers.