The movie portrays
June Gibbons and
Jennifer Gibbons as fraternal or "dizygotic" twins, "non-identical twins", "dissimilar twins" or "biovular twins"; Around two in three sets of twins are fraternal. Two separate eggs (ova) are fertilised by two separate sperm, resulting in fraternal or 'dizygotic' (two-cell) twins. These babies will be no more alike than siblings born at separate times. The babies can be either the same sex or different sexes. Or the 'third-twin type' may play its part here too; Some researchers believe there may be a third type of twin, although medical opinion is still divided. It is proposed that the egg splits in two, and each half is then fertilised by a different sperm. This theory is an attempt to explain why some fraternal twins look identical: June and Jennifer were identical twins.
