Cândido Godói is a village of 7,000 inhabitants in the south of Brazil that has a phenomenal number of twin births.
The rate is ten times higher than the national average, and no one knows why.
A team of geneticists have been working with the community for a number of years, sampling DNA and learning about families, in an effort to solve the mystery.
BBC News went to meet some of the twins and hear more about the village’s history.
Video journalist: Gibby Zobel