Literally the only reason Franz Kafka existed was because his Jewish ancestor was allowed to have a family.
In short, between 1745 and 1859 in the Kingdom of Bohemia (what is now the Czech Republic), there was a law that limited the number of Jewish families. A census taken in 1787 showed that there were 8,541 Jewish families in Bohemia; preferring round numbers, the government increased the limit to 8,600. And for close to a hundred years, that was the limit. If a Jewish man wanted to get married and get a marriage license, he had to emigrate from the country. Otherwise, they had to wait until an existing Jewish father died. Usually, this meant that a son inherited the spot from his father (and wouldn't that cast a fun pall on a wedding, knowing that you can only have it because your father is dead?), but when a married Jewish man died without a son, the spot went up for someone to acquire.
But to apply for the spot, you needed to pay three years taxes, prove that you possessed at least 300 florians, had a school education, pass some exams, and be at least 24 years old.
Franz Kafka's grandfather passed those requirements.
If not for the fact that he did, and that another Jewish man had died without leaving a son behind, there would be no Franz Kafka.