Answer
The answer is Anastasia and Alexei. They were the youngest siblings of Tatiana, the second eldest daughter of Tsar Nicholas II and Empress Alexandra of Russia. Anastasia was born in 1901 and Alexei was born in 1904, making them the youngest of the five imperial children. Tragically, both Anastasia and Alexei, along with their entire family, met their untimely demise during the Russian Revolution in 1918.