Australian doctors discovered extremely rare twins for the first time during pregnancy. These are semi-identical twins, which originate from the same egg, but two different sperm cells. The four-year pregnancy is now described in a medical journal. Traditionally, only two types of multiple births were known: identical and more abundant. In the first case, the ovule cell is divided into two embryos after fertilization, after which two genetically identical children appear. In the second case, several oocytes are fertilized by separate sperm cells. The result is genetically similar to other brethren. In this new case, a bone cell is fertilized by two sperm cells at the same time. As a result, the genetic material that children received from their mothers is 100 percent, that of their father, 78 percent is the same. "It's a crazy intermediate way," says senior article researcher in The New England Journal of Medicine describing the twins. Only one similar case is known, twins who were born in the United States in 2007. This was brought to the attention of the researchers because one of the babies had male and female sex characteristics. In a genetic database with a thousand other twins no similar cases were discovered. The new twins were discovered during pregnancy when they seemed to share a placenta as an identical twin, but they had a different genus, which is not possible with identical twins. The children were born in Brisbane four years ago. According to doctors, one of the children was susceptible to ovarian cancer due to genetic errors and the ovaries were eliminated. In addition, children think it's good. "They are two beautiful children."