Simplify the following text for a Grade 11 native English-speaking person.
Original: DNA and skeletal analysis matched these remains to Tsar Nicholas II , Tsarina Alexandra , and three of the four Grand Duchesses ( Olga , Tatiana and Maria ) .
Simplified: DNA and studies on their skeletons showed that they were the bodies of Tsar Nicholas II , his wife , and three of the Grand Duchesses ( Olga , Tatiana , and Maria ) .