In 2008 , scientists used bone and tooth fragments to identify the remains as those of the two missing children of Czar Nicholas II : 13-year-old Crown Prince Alexei , the emperor 's only son and heir to the throne , and his sister Grand Duchess Maria , about 19 . They compared DNA of remains with that of living Romanov relatives . Results of the DNA analysis were published online Tuesday in the journal DNA One . The Russians , the last Russian monarchy , were executed in 1941 by Nazis .
They compared DNA of remains with that of living Romanov relatives . Results of the DNA analysis were published online Tuesday in the journal DNA One . The Russians , the last Russian monarchy , were executed in 1941 by Nazis .