In 1841 Tyl fell in love with his wife's much younger sister Anna, who was also a talented actress and performed under the pen name Anna Rajská (1824–1903). They started an affair, Tyl did not divorce or leave his wife however and all three of them lived together in one household until his death. Anna bore her brother-in-law eight illegitimate children, their youngest son was born one month after Tyl died. Their sons went by their mother's surname Forchheim, daughters were allowed by the authorities to use father's surname Tyl.