How old were the actors in Můj přítel Fabián (1955)?

The story of a gypsy named Fabian, who came to work in Kunčice, and his son. Their lives change fundamentally on the great construction site of socialism. They both learn to read and write; Fabian becomes a skilled welder, and little Fabian is accepted into the pioneer organization. However, their transformation is not easy, it is not without many encounters, just like the transformation of Fabian's co-workers, many of whom have not yet overcome their racist prejudices.