MODEL RELEASED. Identical twins. Four year old identical twin girls eating healthily. One is eating an apple, while the other is chewing on a carrot. Genetically identical (monozygotic) twins arise when a single fertilised egg from their mother splits into two cells, producing two offspring. Although one twin is often much bigger than the other at birth, they are always of the same sex and look remarkably alike. Fruit and vegetables are high in vitamins and minerals, as well as providing a good source of fibre, which is essential for digestion.