Here's one to get the grey cells working overtime (perhaps!?). Do you know or can you guess who is the odd one out on this list and why? Whilst it is always possible that there may be more than one valid answer you have to get the one I had in mind!
Prince Richard, Duke of Gloucester
Lady Margaret Rhodes
Princess Alexandra, The Hon, Lady Ogilvy
The Hon. John Bowes-Lyon
Prince Michael of Kent.