Diese Nacht ist unsere Nacht (1937)

When upper-class Parisian Charles Dupont and his family hire Tina and Michel as their servants, they have no idea that the domestics are in fact Tatiana, the Grand Duchess Petrovna, and her husband, Mikail, Prince Ouratieff. Recent exiles from the Russian Revolution, Tatiana and Mikail befriend the Dupont family, keeping their true identities a secret -- until one night when Soviet official Gorotchenko arrives for dinner.