As soon as it was announced that Camilla had been awarded it, I reckoned that they would be trying to avoid Queen Elizabeth's faux pas with the Honours of Scotland and that Thistle robes would be the order of the day at St Giles.I don’t think Andrew has ever had it. I assume Edward has been awarded it is because its associated with Scotland and he is the Duke of Edinburgh.
Interestingly, the Princess Royal wore her Thistle robe at the Westminster coronation even though she has the Garter and wore her Garter sash. The King often wears his Thistle sash at Trooping the Colour.