To identify the remains of the Romanovs found in a mass grave, Prince Philip provides a DNA sample, as he is a direct descendant of Tsarina Alexandra's sister.
How did the episode change your perspective on King George V’s legacy? [S5E6] Ipatiev House
For a post about Season 5, Episode 6, titled "Ipatiev House," The Crown S5E6: "Ipatiev House" — Post Breakdown To identify the remains of the Romanovs found
Was the juxtaposition of the Romanov execution with the 1990s Royal Family drama effective or too grim? The Fall of the Romanovs: the Frock Flicks Guide Prince Philip provides a DNA sample
The real Ipatiev House was demolished in 1977 on orders from the Politburo, which claimed the site lacked "historical significance" to prevent it from becoming a shrine.