The essay maps relationships of particular members of the Jirecek family with the architect and patron of the Czech science, Josef Hlavka. It hints on some less known aspects of the Czech Academy of the Sciences and the Arts (CAVU) origin and suggests that the Jirecek family was very friendly with the Hlavka family. Of the Jirecek family, Josef Jirecek was the closest to Josef Hlavka and the person most strongly linked with the establishment of CAVU. His work for the architect and builder Josef Jirecek, his role as Hlavka's expert adviser and lawyer, his considerate influence on Hlavka and empathy with his conditions and problems have not yet received appropriated attention. J. Jirecek participated in preparatory phases of establishing the CAVU: he talked Hlavka out of selling the Luzany estate and thus had merit in maintaining one of the principal sources of its financing. He prepared for Hlavka dedicative documents for establishing a foundation, which supported Czech science and art. Unlike his brother Hermenegild and son Konstantin, Josef Jirecek did not become a member of CAVU, because he died in 1888 and did not live to see its official establishment in 1892. The relation between Josef Hlavka and Hermenegild Jirecek had a character of mutual admiration. Konstantin Jirecek tended to regard the patron of Czech science with disrespect, which is a common practice with young generation.