I believe that four of them have direct descendants sitting on European thrones as reigning monarchs today --

King Frederik VIII: four (Norway, Denmark, Belgium, Luxembourg)

Princess Alexandra: two (Norway, UK)

King George I of the Hellenes: two (UK, Spain)

Princess Thyra: one (Spain)

Is all this correct? Did I miss any? Princess Dagmar would be on the list, but for the fact that the Romanovs of Russia got deposed a long time ago.