In 1826 William was forced to abandon a relationship with Polish noblewoman Elisa Radziwill, his cousin whom he had been attracted to, when it was deemed an inappropriate match by his father. It is alleged that Elisa had an illegitimate daughter by William who was brought up by Joseph and Caroline Kroll, owners of the Kroll Opera House in Berlin, and was given the name Agnes Kroll. She married a Carl Friedrich Ludwig Dettman (known as "Louis") and emigrated to Sydney, Australia, in 1849. They had a family of three sons and two daughters. Agnes died in 1904.