She was born Ingeborg Greta Katerina Marie-Rose Klinckerfuss on April 6, 1918 in Berlin, Germany. At the age of sixteen she dropped out of school to join a local theater troupe. In 1936 she married Arthur Young, a pianist from Scotland. The following year she gave birth to a son named Alastair. Soon after she moved to England leaving her husband and son behind. Kaaren began working as a model in London. Producer Irving Asher saw a screen test she made and put her under personal contract. She made her film debut in the 1939 British drama Ten Days In Paris. Her performance got good reviews and she was offered a contract at MGM. Shortly after arriving in Hollywood she was hospitalized for an appendectomy. Kaaren was given small roles in Sky Murder and The Wild Man Of Borneo. While filming All Through The Night in 1941 she met actor Peter Lorre who was fourteen years older than her and married They began having an affair and filed for divorce from their spouses. She co-starred with Robert Cummings in Kings Row and with Spencer Tracy in The Seventh Cross. On May 25, 1945 she and Peter were married in Las Vegas. He didn’t want her to work so she put her career on hold.