czar

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Nicholas II [Russian: Николай II, Николай Александрович Романов, Nikolai II, Nikolai Alexandrovich Romanov (18 May 1868 – 17 July 1918)] the last Tsar of the Russian Empire with his only son Alexei Nikolaevich Romanov (Russian: Алексе́й Никола́евич) (12 August 1904 – 17 July 1918).

If this picture was from March, 1917, this was probably taken at what was the Russian Army's headquarters in Mogilev, in present-day Belarus, where the Tsar spent long periods as commander-in-chief. He went there on March 7, 1917, during violent riots in St. Petersburg. He was forced to abdicate the throne on March 15, 1917.
en.wikipedia.org/wiki/February_Revolution#Tsar.27s_return...

en.wikipedia.org/wiki/Nicholas_II
ru.wikipedia.org/wiki/%D0%9D%D0%B8%D0%BA%D0%BE%D0%BB%D0%B...
en.wikipedia.org/wiki/Alexei_Nikolaevich,_Tsarevich_of_Ru...

Czarewitch (on the negative here, written Czarewitsch) is an older variant transliteration of Царе́вич, now more commonly written in English as Tsarevitch, meaning any male son of the Tsar.

And see:

Czar of Bulgaria 1908-1918: www.questia.com/library/encyclopedia/ferdinand-czar-of-bu...

Ferdinand I, Tsar of Bulgaria (February 26, 1861 - September 10, 1948), born Prince Ferdinand Maximilian Karl Leopold Maria of Saxe-Coburg and Gotha, was the Knjaz (Prince Regnant) and later Tsar of Bulgaria as well as an author, botanist, entomologist and philatelist. Source: en.wikipedia.org/wiki/Czar_Ferdinand

Here is article about the Czar: en.wikipedia.org/wiki/Czar_Ferdinand

Thanks, Harry! We will add a note to the source data and reload the description.