Heteropaternal Superfecundation is when a woman releases two ova that are fertilized by two different men's sperm presumably in two seperate instances of intercourse in a relatively short period of time resulting in fraternal (non-identical) twins who are half-siblings.
Real Life examples: This has happened twice on the Maury Povich show during his baby paternity episodes. In typical fashion a woman brings a man to the Maury Povich show and shouts at him about being the father of the twins. The guy comes out and shouts that he isn't. Turns out they're both wrong and he's the father of only one of them.
- A news item in 2009 reported a texas woman named Mia Washington gave birth to twins from different fathers. She and her partner James Harrison got suspicious when one of the twin boys didn't resemble him. She eventually admitted to an affair with another man.
- Heracles and his twin brother Iphicles. Heracles's human mother Alcmene gave birth to twins. Her son Iphicles was the son of her human husband King Amphitryon and Heracles who was the son of the Greek god Zeus.
- In some accounts the god Zeus is the father of two of the human princess Leda's quadruplets. One night he came to Leda as a swan. Leda gave birth to four eggs from which hatched her four children Castor & Pollux (the twins we name the constellation Gemini after), Helen of Troy and Clytemnestra. Zeus is the father of Castor and Helen. Leda's husband Tyndareus is the father of Pollux and Clytemnestra. Pollux being Zeus's son is immortal while his brother Castor is not. Helen the face that led to the Trojan War is also Zeus's while Clytemnestra (mother of Electra) is Tyndareus daughter.
- twins Tommo and Hawk Solomon in Bryce Courtenay's Australian Trilogy
- Anime examples:
- Boku wa Imōto ni Koi o Suru - twins Yori and Iku have different fathers.
Live action Television examples:
This has been a plot on at least 3 soap operas but it was retconned away on one of them.
- One Life To Live- It is revealed that Victoria Lord (who has multiple personality disorder) was raped by villain Mitch Lawrence. She became pregnant with twin girls, one was her daughter Jessica by Mitch and the other daughter Natalie by her husband Clint. Mitch kidnapped Clint's daughter Natalie and her raised by another family while his child Jessica was raised by Clint and Victoria. Years later Mitch marries a grown up Natalie (the half sister/twin of his daughter) in a bizarre revenge plot to steal Victoria's fortune.
- Days of Our Lives. Sami Brady is raped/coerced into sex by EJ Dimera while she is married to Lucas Roberts. She later gives birth to twins John and Alice. John is EJ's son while Alice is Lucas daughter. Later in typical soap fashion Sami falls in love with her rapist EJ and has another daughter with him.
- Guiding Light. Blake Thorpe Marler gave birth to fraternal twin boys Jason and Kevin. Blake discovered that her son Kevin was fathered by her lover Rick Bauer but Jason was fathered by her husband Ross Marler. It was eventually revealed that another character who worked at the hospital swapped dna results to make it appear that Rick was Kevin's father but in fact both twins were fathered by Blake's husband.