This can be dated by the Russian pages to the time of Nicholas II's coronation in 1896. Their mother, Grand Princess Maria Alexandrovna, was a member of the Romanov family.
From www.pinterest.com/fedecapocchi/crowned-people; image cropped to remove flaws on right side and sepia tone removed.
Ducky's dress has a vee waistline and hourglass figure while Marie's has a blouson bodice. Ducky's sleeves appear to be adorned with flounces.
Keywords: Marie of Romania, Missy, Victoria Melita, Ducky, Welf family, Wettin family, Hohenzollern family, Hesse family, Romanov family, Princess, Queen, Grand Duchess, Grand Princess, curly coiffure, tiara, square neckline, epaulettes, quarter length puffed sleeves, flounces, blouson bodice, waist band, vee waistline, A-line skirt, train, shoes, floral bodice ornament, necklace, earrings, bracelets