In Russia, the practice of royal intermarriages was introduced by Peter the Great when Tsarevich Alexei Romanov married the Princess of Brunswick-Wolfenbüttel in 1711.

The parents of Charlotte Christine Sophie (1694–1715) were Duke Ludwig Rudolf of Brunswick-Wolfenbüttel and Christine Louise of Oettingen-Oettingen. For many years the princess lived at the court of her relative, the King of Poland Augustus II. How undesirable her marriage to the Russian tsarevich was can be judged by the letter to her grandfather, Duke Anthony Ulrich: “The Moscow proposal may still pass me by. I still hope for that.”

However, Augustus II and Peter I were interested in strengthening ties between the states and demanded a written promise from Charlotte to fulfill their will.

Alexei was a follower of old Russian traditions, and just like him, a significant part of the Russian people, did not accept Peter’s decision to allow the foreign princess to retain her faith — Lutheranism.

Four days after the wedding, by order of Peter I, Alexei was to go to Torun to oversee the food supply of the Russian troops. The historian Alexey Vladimirovich Morokhin wrote that this episode was the reason for the first argument between spouses. Despite this, in 1712, the Crown Princess wrote to her father from Torun that she was “quite happy”.

Three years after the marriage, Charlotte gave birth to daughter Natalia, and a year later — to son Peter, already knowing about the husband’s affair with the serf-girl Yefrosinya. When the baby was ten days old, the Crown Princess died of puerperal fever, entrusting the children to her father-in-law, Peter I. Two years later, the disgraced Tsarevich Alexei died in the Peter and Paul Fortress.