The scientific term describing fraternal twins by different fathers is heteropaternal superfecundation. While this is the rarest form of twins it is a scientific possibility & has happened (documented) before.
1).Twins with different fathers [letter]., Verma RS; Luke S; Dhawan P, Lancet 1992 Jan 4; 339 (8784): 63‑4
2).Another case of occurrence of two different fathers of twins by HLA typing., Majsky A; Kout M, Tissue Antigens 1982 Oct; 20 (4): 305
3).Twins with two different fathers identified by HLA., Terasaki PI; Gjertson D; Bernoco D; Perdue S; Mickey MR; Bond J, N Engl J Med 1978 Sep 14; 299 (11):590‑2
Fraternal Twins with Different Fathers
Cannot be excluded as the mother of either of the twins.
Excluded as father of Twin 2 on both genes.
Excluded as father of Twin 1 on ABO gene.
In Brooklyn NY, the husband of a woman who had non‑identical, different sex twins accused another man (alleged father) of being the father of the twins. The alleged father denied the accusation and refused responsiblity for the children. The alleged father was homozygous for a rare chromosomal polymorphism on chromosome 18 (Alu1 resistant chromatin) and was homozygous for blood type "s" (ss genotype). The male twin was heterozygous for the chromosomal polymorphism on chromosome 18 whereas the female twin was homozygous for blood type "S" (SS genotype). Thus, the alleged father could have produced the male twin but could not have produced the female twin. The husband refused to be tested.
Lancet 239:63, 1992
A woman in China gave birth to non‑identical, different sex twins. The husband discovered that the mother was having intercourse with another man and refused responsibility for the children. Testing of blood type and enzyme markers are shown below:
The husband was excluded as the parent of the twin boy on four of the genetic markers (shown in bold face in the table). The probability of his being the father of the twin girl was calculated to be 99.23%. Confronted with the evidence, the mother admitted to having sexual intercourse with both men within a three day period at the time of conception. J. Forensic Sci.39:1100, 1994
Also in China, a married man had a mistress who became pregnant and delivered non‑identical, different sex twins. When she accused him of non‑support, he denied being the father of the twins. Testing of blood type and enzyme markers are shown below:
The man was excluded as the parent of the twin girl based on the HLA markers alone (shown in bold face in the table). The probability that he was the father of the twin boy was calculated to be 99.28%. The mother admitted to having sexual intercourse with another man within a few days of the time of conception. J. Forensic Sci.39:1100, 1994
An unmarried woman who had non‑identical twins (sex not mentioned) accused a man of being the father (Putative Father 1 or PF1. Test results of the three HLA loci are show below:
This initial testing suggests that PF1 could be the father of twin 1 (probability of 98.1%) but he could not be the father of twin 2. The mother was confronted with this information and she named another man as Putative Father 2 (PF2). More complete genetic testing was done on all individuals.
Based on the data for Rh, PF1 could not be the father of Twin 2 and PF2 could not be the father of Twin 1. Based on the data for Hp (haptoglobin), PF2 could not be the father of Twin 1. The HLA typing also indicates that PF1 could be the father of Twin 1 but not the father of Twin 2 and that PF2 could be the father of Twin 2 but not the father of Twin 1. The probability that both twins were fathered by a third (unnamed) man was 1/140,000 or 0.0007%. New Engl. Journ. Med. 299: 590, 1978
Case Seven: Four Parents: One Pregnancy: Two Non ‑ Twin Babies
The Gemini twins, Castor and Pollux, were born by Leda and fathered by Tyndareus and Zeus, respectively.
This document maintained by Robert J. Huskey Last updated on April 8, 1999.