Most identical twin births in an extended family pedigree

A family in Jordan has reportedly produced 17 identical twin pairs born within five generations. This is the highest number of identical twins born within an extended family. The family members are known to share a particular allele or form of the ELA gene. This particular gene is expressed within the mass of cells that give rise to the early embryo and foetal structures. This gene is suspected of promoting identical twinning. The common wisdom for many years had been that the predisposition for having fraternal (non-identical) twins was genetically passed down in families, and that identical twins occurred randomly among individuals. However, the new research is now challenging these suppositions. There may be two types of identical twins – one with genetic origins occurring in selected families, and another that does happen by chance.