<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (May 2009) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (May 2009) (Learn how and when to remove this template message) </Td> </Tr> <P> Superfecundation is the fertilization of two or more ova from the same cycle by sperm from separate acts of sexual intercourse, which can lead to twin babies from two seperate biological fathers . The term superfecundation is derived from fecund, meaning the ability to produce offspring . Heteropaternal superfecundation refers to the fertilization of two separate ova by two different fathers . Homopaternal superfecundation refers to the fertilization of two separate ova from the same father, leading to fraternal twins . While heteropaternal superfecundation is referred to as a form of atypical twinning, genetically, the twins are half siblings . Superfecundation, while rare, can occur through either separate occurrences of sexual intercourse or through artificial insemination . </P> <P> Superfecundation most commonly happens within hours or days of the first instance of fertilization with ova released during the same cycle . The time window when eggs are able to be fertilized is small . Sperm cells can live inside a female's body for four to five days . Once ovulation occurs, the egg remains viable for 12--48 hours before it begins to disintegrate . Thus, the fertile period can span five to seven days . </P>

Is possible for twins to have different dads