On the DNA Testing of Mr. Miyuji and Mr. Nora

Rewritten on: December 6, 2024

A DNA sibling test between Mr. Nora, who claims to be the son of Masahiro Kuwana, and Mr. Miyuji reportedly produced a result of "95% not brothers." However, a male-to-male half-sibling test should normally yield a clear-cut result of either 0% or 99.9%+, and an expert explains this case, in which the reliability of the testing is called into question.

The DNA Sibling Test Between Mr. Miyuji and Mr. Nora — The Truth Behind the "95% Not Brothers" Result

On February 25, 2019, the result of a DNA sibling test between Mr. Nora, who claims to be the son of the late Masahiro Kuwana, and Mr. Miyuji, known as Kuwana's eldest son, was reported [ref:1]. The test result was reported as "95% not brothers," and many media outlets reported that "Mr. Nora was not, after all, the biological child of Masahiro Kuwana" [ref:2]. However, from the standpoint of a DNA testing expert, this figure of "95% denial" raises serious questions. This article explains in detail why this result is questionable, and what result should actually be obtained from a proper sibling test.

Is "95% Not Brothers" Really an Accurate Result?

According to reports, the testing institution stated that a figure of "95% not brothers" — essentially meaning "no blood relationship whatsoever" — had been reported [ref:2]. This led to the widely circulated conclusion that "Mr. Nora was indeed not the biological child of Masahiro Kuwana." However, from a professional DNA testing standpoint, this figure itself is highly unnatural.

First, in DNA testing, the probability of a blood relationship varies greatly depending on the relationship between the subjects and the number of people who can participate in the test. It is true that intermediate figures in the 5–95% range do occur in certain cases. This phenomenon is seen in tests between siblings of different sexes, or in DNA testing examining grandparent–grandchild relationships. In such cases, because the shared DNA regions are limited, it can be statistically difficult to reach a clear conclusion.

The Result Expected From a Male-to-Male Half-Sibling Test

However, this test was between two half-brothers (paternal or maternal half-siblings) who are both male. In a male-to-male half-sibling test, Y chromosome analysis is an extremely powerful means of determination. Because the Y chromosome is passed down from father to son with almost no mutation, males who share the same father will have matching Y-STR (short tandem repeat) profiles [ref:3].

In other words, if two men share the same father (Masahiro Kuwana), a match in Y-STR type should confirm the blood relationship with a probability of 99.9% or higher. Conversely, if the fathers differ, the Y-STR types will clearly not match, resulting in a 0% result — that is, "exclusion" (a complete denial of the blood relationship).

In this way, male-to-male half-sibling tests normally produce a clear "black or white" result, and an ambiguous figure such as "95% denial" should not ordinarily occur.

Sibling Test Result Patterns (Between Males)

A One-Month Testing Period — Hard to Imagine From a Trustworthy Testing Institution

Another point that raises doubts about this test is the fact that it took about a month for the results to come out. Generally, at reliable DNA testing institutions, even a blood relationship test such as a sibling test yields results within about one to two weeks. Even including sample collection, DNA extraction, PCR amplification, electrophoresis analysis, and statistical processing of the data, the process can technically be completed in around a week.

The fact that it took as long as a month suggests the possibility of problems with the testing institution's technical capability or equipment, or possible deficiencies in sample handling or analytical methods. DNA testing is an examination that requires a high degree of specialized knowledge and appropriate equipment, and the length of the testing period is one indicator of a testing institution's reliability.

How Confidentiality and Result Notification Work in DNA Testing

DNA testing is subject to strict rules from a privacy protection standpoint. Test results are not disclosed even to the subjects who participated in the test, unless the client consents. This is because DNA information is extremely sensitive personal information, and because test results can have a serious impact on the lives of those involved [ref:4].

For this reason, outside third parties normally cannot know the detailed content of a test. In this reported case as well, it has not been disclosed what testing items or statistical methods were used to calculate the "95% denial" figure. Of course, the possibility that Mr. Nora's father is someone other than Masahiro Kuwana cannot be ruled out, but neither can the possibility that this DNA test itself was a misjudgment by a provider lacking the necessary expertise.

What's Needed to Get a Clear-Cut Answer

To resolve an ambiguous result like this one and arrive at a clear black-or-white answer, a retest meeting the following conditions is necessary.

1. All of Mr. Miyuji's siblings participate in the test
2. A comprehensive analysis including Y chromosome STR testing is performed
3. The test is commissioned to a highly reliable, specialized testing institution
4. The likelihood ratio is calculated using an appropriate statistical method

If a proper test is conducted meeting these conditions, a clear result can be obtained in about a week. In a male-to-male half-sibling test, Y chromosome analysis can determine a clear "match" or "non-match" in black-and-white terms.

The Importance of Choosing a Testing Institution — Beware of Providers Lacking Expertise

Unlike a simple paternity test (a three-way test involving father, mother, and child), indirect blood relationship tests such as sibling tests or grandparent/grandchild tests depend directly on the testing institution's expertise for the reliability of the results. Paternity tests can be judged through relatively simple comparison of matching alleles, but sibling tests require complex statistical calculations based on the frequency of shared gene loci, and must also combine analysis of the Y chromosome and mitochondrial DNA [ref:5].

To choose a reliable DNA testing institution, it is important to check the following points.

• Whether the company operates its own dedicated genetic analysis laboratory
• Whether the staff involved in testing have received specialized education in genetics
• Whether the institution holds international accreditation such as ISO17025
• Whether the testing period falls within a reasonable range (typically 1–2 weeks)
• Whether the result report clearly states the testing methods and statistical basis
• Whether it is an actual testing laboratory that handles DNA directly, rather than a broker

In reality, there are cases where brokers with no expertise — who have never even handled DNA themselves — merely accept the request and outsource the analysis to an external party. With such providers, there is a risk of various problems, including sample mix-ups, degradation due to improper storage, and misreading of analysis results. Because DNA testing is a critical examination that can affect a person's life, it is essential to consult a trustworthy testing institution.

The Basic Mechanics of DNA Sibling Testing

To explain the basic mechanics of DNA sibling testing simply: DNA is first extracted from samples collected from the subjects (such as oral mucosa cells or blood), and specific gene loci are amplified using the PCR method. Next, multiple STR (short tandem repeat) loci on the autosomes are analyzed, and the degree to which gene loci are shared between the two subjects is statistically evaluated [ref:3].

When both subjects are male, Y chromosome STR analysis is also performed, allowing a highly accurate determination of paternal-line match or mismatch. Because the Y chromosome is passed down as a single unbroken line from father to son, male siblings who share the same father will have completely matching Y-STR profiles. Thanks to this characteristic, even in cases where autosomal analysis alone makes it difficult to reach a determination — such as testing between male half-siblings who share the same father but have different mothers — adding Y chromosome analysis can produce a clear conclusion [ref:6].

Summary

The "95% not brothers" result from the DNA sibling test between Mr. Miyuji and Mr. Nora is an unnatural figure for a male-to-male half-sibling test, and questions remain about the accuracy and methodology of the testing. In addition, the fact that it took a month to produce results is also hard to reconcile with the standards of a professional testing institution. Because DNA testing is an examination that can greatly affect a client's life, choosing a testing institution with genuine expertise and reliable technology is of the utmost importance. If you are considering a DNA test for a blood relationship, we strongly recommend consulting a highly reliable, specialized institution with its own in-house laboratory, rather than a broker.

Frequently Asked Questions

Q1. Is a "95% denial" result common in DNA sibling testing?

A. No. In a male-to-male half-sibling test, Y chromosome analysis normally produces either a "complete match (99.9%+ confirmation)" or a "complete non-match (0%, exclusion)." An intermediate figure such as 95% denial can sometimes occur in tests between siblings of different sexes or in grandparent/grandchild tests, but in this case it is an unnatural result.

Q2. How long does it normally take to get results from a DNA sibling test?

A. At a reliable testing institution, results are normally available within about one to two weeks. This period includes everything from sample receipt through DNA extraction, PCR amplification, analysis, statistical processing, and report preparation. If it takes more than a month, there may be problems with the testing institution's equipment or technical capability.

Q3. What's the difference between a sibling test and a paternity test?

A. A paternity test directly compares matching and non-matching alleles, so relatively simple analysis can produce highly accurate results. A sibling test, on the other hand, is an indirect blood relationship test that requires statistically evaluating the frequency of shared gene loci, demanding a higher level of specialized knowledge and analytical technique.

Q4. Are DNA test results disclosed to anyone other than the person themselves?

A. No. Without the client's consent, DNA test results are not disclosed even to the subjects who participated in the test. Because DNA information is extremely sensitive personal information, strict privacy protection rules apply.

Q5. What should I look for when choosing a reliable DNA testing institution?

A. Important criteria include whether the company has its own genetic analysis laboratory, whether testing staff have received specialized education in genetics, whether it holds international accreditation such as ISO17025, whether the testing period is reasonable (1–2 weeks), and whether the result report clearly states the testing methods and statistical basis. We recommend commissioning the test directly to an actual DNA testing laboratory rather than a broker.

Q6. What is Y chromosome STR testing?

A. This is a test that analyzes the length of repeating sequences called STRs (short tandem repeats) present on the Y chromosome. Because the Y chromosome is passed from father to son with almost no mutation, males who share the same father will have matching Y-STR types. This characteristic makes it possible to determine paternal-line blood relationships between males with high accuracy.

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