In Galician, Portuguese and Brazilian folklore, it is the seventh of the sons (but sometimes the seventh child, a boy, after a line of six daughters) who becomes a werewolf.
In some Latin American countries, the seventh sons of a seventh son is believed to be cursed to be a werewolf, lobizón, Luison (in Paraguay) or lobisomem. To prevent this, the newborn should be baptized in seven different churches.
Alternately, he may be baptized under the name Benito, with his eldest brother (the eldest son of their father) as his godfather.
This belief was so extended in Northern Argentina (where it is called the “lobizon”), that seventh sons were abandoned, ceded in adoption or killed.
A law from 1907 decreed that the President of Argentina is the godfather of every seventh son. Thus, the State gives him a gold medal in his baptism and a scholarship until his 21st year. In 1973, the presidential adoption tradition was also extended to seventh daughters.
This ended the abandonment, but it is still traditional that the President godfathers seventh sons.