Sir

In his Correspondence 'You're the best man for this job, son. What a coincidence!', Albert Ruggi's suspicions about the process by which the offspring of professors are deemed to be the best candidates for new positions may well be justified (Nature 456, 870; 2008). On the other hand, a few rare families just do produce generations of eminent scientists. For example, there are at least seven parent–child pairs of Nobel laureates.

Four of these were in physics: the Thomsons (J. J. in 1906 and George in 1937), Braggs (William and Lawrence together in 1915), Bohrs (Niels in 1922 and his son Aage in 1975) and Siegbahns (Manne in 1924 and his son Kai in 1981). Marie Curie and her daughter Irène Joliot-Curie both won the Nobel Prize in Chemistry (1911 and 1935), after Marie and her husband, Pierre, had won the physics Nobel in 1903.

The Kornbergs branched out more (Arthur, physiology or medicine, 1959; Roger, chemistry, 2006), as did Hans von Euler-Chelpin (chemistry, 1929) and his son Ulf von Euler (physiology or medicine, 1970).