Egg and sperm donors in the UK who donate through gamete banks or fertility clinics are only supposed to provide samples to a maximum of ten families.
However, data from the Human Fertilisation and Embryology Authority (HFEA) show that over 1500 donors have contributed to the births of 12 or more children, and over 100 have 20 donor offspring. Four individuals have also been linked to the births of over 40 children.
Rachel Cutting from the HFEA told the Sun that breaches of the ten-family limit are very unusual and 'are often only just over'.
Read more here.