Ilse Einstein: Einstein Liked to Marry His Fiancé’s Daughter

However, Ilse held Einstein in a place of near-paternal regard.

By Hrothsige Frithowulf - History Editor
Ilse Einstein (left) and Margot Einstein, at Caputh's house, 1929.
Ilse Einstein (left) and Margot Einstein, at Caputh's house, 1929.
  • Einstein contemplated marrying his future stepdaughter, Ilse, in 1918.
  • Ilse Einstein considered Albert more of a father figure.
  • Einstein later saw Ilse and Margot as his own daughters.

Although Albert Einstein spent the years 1914–1918 working tirelessly on his groundbreaking theory of relativity, his personal life was becoming more complex. Einstein’s thinking of marrying his cousin-wife Elsa‘s daughter Ilse in 1918 is interesting on its own. Ilse Einstein (1897–1934) was the daughter of Elsa and her previous husband, Max Löwenthal. In 1919, she became the stepdaughter of Albert Einstein, then a nationally renowned figure.

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Background to the Story

Elsa married the Berlin textile merchant Max Loewenthal (1864–1914) in 1896. Ilse (1897–1934) and Margot (1899–1986) were born and raised in Hechingen. Max Loewenthal moved to Berlin for professional reasons in 1902. Their home was in Hechingen. In 1903, they had a son, but he passed away shortly after birth. Elsa moved to Berlin’s Haberlandstrasse 5 with her two daughters after her marriage ended in 1908. Around 1912, she and Albert Einstein, childhood cousins, began dating in Berlin.

Ilse Einstein's mother Elsa Einstein and Albert Einstein
Ilse’s mother Elsa, and Albert Einstein.

When Einstein confessed his feelings for Ilse, his fiancée’s daughter, in the spring of 1918, the twenty-year-old lady was thrown into a state of confusion. She sent a personal letter to her family’s friend, Georg Nicolai, explaining her predicament and asking for guidance.

“I have never felt the desire or the slightest desire to be physically close to him.”

Ilse confessed to Nicolai in May 1918.

Einstein’s Complex Relationships

At the age of 38, Einstein had relocated to Berlin in 1919 and divorced Mileva in preparation for his upcoming marriage to his cousin Elsa. Einstein’s assistant at the time was Ilse, Elsa’s oldest daughter, and Albert was already engaged to Elsa.

After a playful remark turned into a serious proposal from Einstein to marry his secretary and future stepdaughter Ilse, instead of her mother, Ilse wrote to her close friend Georg Nicolai for advice, with a note “destroy after reading.” Nicolai had been her ex-lover.

Picture shows Ilse Einstein, the stepdaughter of Albert Einstein, sailing. She went on a boat trip with her husband, her mother, and her stepfather.
Picture shows Ilse Einstein sailing. She went on a boat trip with her husband, her mother, and her stepfather Einstein. (Image: Leo Baeck Institute, F 38590)

Einstein told Ilse that he loved her, but she didn’t openly return her sentiments (or it was never documented). It was because of this that Einstein was thinking of ending his engagement to his cousin Elsa right away.

However, it appears that she loved Einstein as a father figure, and she had no interest in having a sexual relationship with him. Fortunately for Albert, there is no indication that their relationship has progressed any further. Months later, Einstein married Elsa, and Ilse later married Rudolf Kayser in 1924.

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Ilse Einstein died of tuberculosis either in 1933 or 1934. Only two years later, Rudolf married Eva Urgiss. Rudolf also wrote a biography of Albert.

Ilse’s Conflicted Emotions

While Ilse held Einstein in a place of near-paternal regard, she did not want to develop romantic feelings for him since she considered herself too young for such a relationship. Albert was 18 years older than Ilse, and Ilse was 20 or 21 years old at the time. However, such an age difference in marriage was not uncommon at the time, and Ilse’s ex-lover, Georg Nicolai, was also older than her.

From the letters sent by Ilse, her mother Elsa was also willing to give up her position of marriage to Einstein if it would make Ilse happy.

Einstein’s Marital Dynamics

einsteins house in berlin
Albert Einstein’s house in Berlin, Caputh. (Photo, Stephan M. Höhne, CC BY-SA 3.0)

Beyond his scientific genius, Einstein was a complex man who had complicated relationships with various women. This can be understood in various ways; his daughter Lieserl Einstein was kept hidden from the public for 85 years, and Evelyn Einstein was possibly Albert’s out-of-wedlock daughter from an alleged New York ballet.

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The Einsteins created a loving family unit with their stepdaughters, Ilse and Margot. Albert raised Ilse and Margot as his own, despite the fact that he and Elsa never had any biological children. They were Berliners who bought a vacation home in Caputh, a suburb of Potsdam, in 1929. During that time, Ilse appears to continue to work as Einstein’s secretary.

However, the vacation house’s architect, Konrad Wachsmann, later reported that there were also recurring scenes of jealousy involving Elsa, where she even mentioned a separation from Albert. But Elsa eventually came to terms with her husband’s behavior. She later explained her predicament:

“It’s not ideal to be the wife of a genius. Your life is not yours to control. It appears to be shared property.”

Elsa was by Einstein’s side until the day she passed away in 1936.