Whether Max Brod had children is an interesting question, because it would considerably complicate the legal battles over the ownership of Kafka's papers. It does not appear that he had any children with his wife. However, he was a notable womanizer, as it was politely termed in his period, and may have had several sexual relationships outside marriage.
Perhaps the most important of his relationships was with Esther Hoffe, his secretary. He seemed to have something approaching a ménage à trois with Esther and her husband Otto, with Esther doing much secretarial work in Brod's apartment and Brod often staying at the Hoffe house and vacationing with the Hoffes. Some acquaintances claim that the relationship between Brod and Esther was sexual, but Esther's daughters deny this.
Thus all we can really conclude is that Brod had no legitimate children in his marriage and no other people have stepped forward to claim him as a parent.