Superfecundation is the fertilisation of two or more ova from the same cycle by sperm from separate acts of sexual intercourse. The term is also sometimes used to refer to the instances of two different males fathering fraternal twins, though this is more accurately known as heteropaternal superfecundation. This therefore leads to the possibility of twins also being half-siblings. This way of formation of multiply pregnancy aroused and it arouses still among doctors on whole world. This problem aroused large interest also among Polish doctors. For example, we found mention of superfecundation in first Polish medical journal, in Primitiae physico-medicae..., given in Leszno in years 1750-1753. Authors introduced relate opinion of superfecundation in aetiology of multiple pregnancies in historical aspect, as early as from Old Testament to present times as well as current state of medical knowledge of such a situation.