Konstantin Makovsky, The Russian Bride's Attire Beneath the Crown, 1889
The story of the marriage of Maria Miloslavskaya to Czar Alexis in 1648 was a well-known tale in Russian history. Here is the Wikipedia account of her marriage to the Czar:
“In 1647, Czar Alexis I of Russia reached the age required for marriage. The tsar was to choose his bride from a bride-show of hundreds of daughters of the nobility, who were summoned to the imperial court for selection. This method to select a bride for the tsar reportedly originated from the reign of Ivan III.
“The bridal selection of Alexis I was managed by Boris Morozov, who gathered together almost two hundred daughters of the nobility, among them Maria Miloslavskaya. She had the support of Boris Morozov, who intended to marry her sister Anna Miloslavskaya, and hoped that Alexis I would choose Maria, which would make him the brother-in-law of the tsar. During the selection ceremony, however, the tsar chose Euphemia Fedorovna Vsevolozhskaya, by presenting her with a handkerchief and a ring as a symbol of their engagement. Boris Morozov then bribed a courtier to make Vsevolozhskaya faint; he then bribed a court physician to diagnose her with epilepsy. This disqualified Vsevolozhskaya as tsaritsa and resulted in both her and her father to be exiled accused of attempting to hide her illness for the tsar, and thus the first choice of the tsar was annulled."
Some commentators see dejection in Maria's face, and sympathy in the countenance of her Sister Anna. More likely she has assumed an attitude of seriousness, with perhaps a foreshadowing of her fate: she would die giving birth to her thirteenth child in 1669.
The man in the doorway might be the groom-to-be Czar Alexis, but more probably it is the marriage broker/manipulator Morozov:
“Maria Miloslavskaya was selected as the tsar's second choice. She was reportedly a beauty, and was declared perfectly healthy after an examination by a court physician. Ten days after the wedding of the tsar to Maria Miloslavskaya, Boris Morozov married her sister Anna Miloslavskaya, making him brother-in-law to the tsar and strengthening his power at court.” — Wikipedia