Crown Prince Alexei was the heir to the throne
Scientific tests have confirmed that bones found last year in Russia belong to the two missing children of Tsar Nicholas II, Russian officials say.
DNA tests carried out in the US showed the remains are those of Crown Prince Alexei and his sister Maria.
The Tsar and his family were shot dead by Bolshevik revolutionaries in 1918, in the Ural city of Yekaterinburg.
The children's remains are expected to be buried with the rest of the Imperial family in St Petersburg.
Nicholas II, his wife Alexandra and their five children - Alexei, Anastasia, Maria, Olga, and Tatiana - were shot dead in the basement of a house in Yekaterinburg after the Russian revolution.
Attempts were made to destroy their bodies with acid, and they were then dumped in a pit.
After the collapse of Communist rule, the remains of most of the family were found and identified.
They were buried in the imperial crypt at St Peter and Paul Cathedral in St Petersburg in 1998.
However two of the children - Alexei and Maria - were missing, and there had been some speculation that they have survived.
Now fragments found last year at the same site have been tested by a genetics laboratory in the US.
"We received full confirmation that they do belong to the Tsar's children," Eduard Rossel, governor of the Sverdlovsk region, told Russian television.
"So now we have found the entire family," he said.