Paternity test finds twins have different fathers


Twin girls in Passaic County share one mother but have different fathers, a state judge has found in a case that defies the laws of probability.

Ruling Monday in a dispute over child-support payments, state Superior Court Judge Sohail Mohammed said DNA testing had revealed the mother – identified as T.M. in court papers – gave birth to “heteropaternal dizygotic twins” in 2013, or non-identical twins by two different men. As such, the one identified father will pay support only for his child.


The uncanny birth did not involve any special medical techniques — just a case of heightened fertility and intercourse with two men in the same week, the judge said.

Doctors and researchers have been aware of the phenomenon since the 1970s. But it is so rare that one of the leading DNA testing experts in the country, Karl-Hans Wurzinger of the lab-testing giant LabCorp, told the court he only sees six cases per year.


In 1997, the incidence rate of twins from different fathers was one out of every 13,000 paternity cases, or 0.008 percent, Mohammed said. That makes it the same odds as sinking a hole-in-one while golfing.

There is no database keeping track of such births, but the phenomenon appears to be on the rise now with the advent of modern reproduction techniques, Mo­ham­med wrote.


“Today, it is believed that the incidence of bipaternal twins is increasing at a higher rate compared to 50 years ago mainly due to assistive reproductive technologies, ovulation induction, promiscuity and other factors,” Mohammed wrote.

The case began in October, when the Passaic County Board of Social Services filed an application to establish paternity and child support for T.M.’s twin daughters, who are now 2 years old. At the time, the mother named a former romantic partner, identified only as A.S., as the father of both girls.

A subsequent DNA test found that he had fathered only one of the girls.


“The mother testified that within about a week, she had sexual intercourse with two men – A.S. and another man,” Mohammed wrote, adding that the other man had not undergone a DNA test.

Although it is rare, some women experience heightened periods of fertility in which they ovulate twice in a space of 48 to 72 hours, experts said. When that happens, it is “entirely possible that each of the eggs could [be] fertilized by sperm from a different man” during separate acts of intercourse, according to Wurzinger, an expert in the field with 25 years of experience in DNA testing.


New Jersey courts had never seen a case like it before, Mohammed said, and in the United States, only two other cases, in Colorado and New York, have dealt with bipaternal twins.

Mohammed, appointed to the bench by Governor Christie, ruled that A.S. must pay $28 a week in support for his child, and the judge declined a request from the Passaic County Board of Social Services to terminate the case, saying paternity had not been established as to the other child.

Because bipaternal twins are so rare, the judge said he reviewed the lab’s DNA testing process exhaustively, including the methods, conditions, technology, training levels of employees and other issues. Mohammed said he was satisfied that New Jersey had “stringent protocols” in place for DNA tests.


“Given the rarity of this medically acceptable phenomena coupled with the general public’s lack of awareness, it is not unreasonable to expect that when one is confronted with the DNA test results that show each twin in a given case has a different father, an overwhelming majority will likely express sheer disbelief,” he wrote.

A.S. represented himself in the case. The Passaic Board of Social Services, which represented the mother, could not be reached for comment.



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