Looking at the Bowes-Lyon family tree, Lord Colin's parents (The Duke & Duchess of Argyll) have so many children and descendants that if one of them had taken an Ancestry test, wouldn't I expect to see a DNA match? I'm wondering whether it's one of these conventions that either the nobility just don't do them or if they do, they have a way to request keeping the results private? I guess relationships like this are exactly what they would not want to find! And all the legitimate ones are already well documented, so why ever take a test...?