Simplify the following text for a Grade 11 native English-speaking person.
Original: DNA testing by multiple international laboratories such as the Armed Forces DNA Identification Laboratory and Innsbruck Medical University confirmed that the remains belong to the Tsarevich Alexei and to one of his sisters , proving conclusively that all family members , including Anastasia , died in 1918 .
Simplified: Many international laboratories such as the Armed Forces DNA Identification Laboratory and Innsbruck Medical University did DNA tests . They proved that the remains were from the body of Tsarevich Alexei and one of his sister .