Tsesarevich was the title of the heir apparent or presumptive in the Russian Empire. It either preceded or replaced the given name and patronymic.
After Jean Louis Voille Paul I, Emperor of Russia, when Grand Duke of Russia RCIN 404631 Royal Collection
Alexander I of Russia by J.Gerin
Grand prince Alexander Nikolaevich
Alexei Nikolaevich was the last Russian tsesarevich. He was the youngest child and only son of Tsar Nicholas II and Tsarina Alexandra Feodorovna. He was born with haemophilia, which his parents tried
Tsesarevich
…the title upon his oldest surviving brother Michael Aleksandrovich, although Nicholas's only son would not be born for another five years. That son, Alexei Nikolaevich (1904–1918), became the Russian Empire's last tsesarevich. The wife of an heir-tsesarevich bore the title Tsesarevna (Russian: Цесаревна) – Grand…
Alekszej Nyikolajevics orosz nagyherceg
Alexei as an infant in 1904
Alexei (right) with his sailor nanny Andrei Derevenko aboard the Imperial yacht Standart in 1908