Wow!  The amount of Eastern European varies from 54% to 63%.  These are verified full siblings – meaning that they had the same parents.  What has obviously happened is that each sibling inherited different DNA from each parent, which is what always happens.  Some DNA is always lost from each parent, no matter how many children that they have.  If you are interested in doing a DNA test for ethnicity purposes, it is really helpful to have your siblings or parents do the test, as well.
What we would expect to find then in this example is that the two descendants of John show a very close match, and the two descendants of James also show a very close match (because we know from conventional paper based research that they are related). If all four match very closely, then that’s further evidence to add to our theory that John and James were really brothers. Not conclusive proof- but pretty solid evidence.
More controversially, some of these kits profess to tell you your biological (as opposed to actual age) by measuring the length of your telomeres (in basic terms, the caps at the end of each strand of DNA that protect chromosomes, like plastic tips at the end of shoelaces). Other tests, such as 23andMe, predict higher risks of developing serious conditions, such as multiple sclerosis, Alzheimer’s and Parkinson’s, including the test for BRCA1/BRCA2 (breast and ovarian cancer) that Angelina Jolie famously underwent, going on to have a preventative double mastectomy and surgery to remove her ovaries.
Although the project states that most participants won’t receive any useful information, patients will be told if something is found in their genome that is relevant to the treatment, explanation or diagnosis of their condition. They can also choose to learn if they have a genetic risk factor for another disease, such as the BRCA1 gene mutation that can cause breast cancer. Genomics England will only look for risk factors that are linked to a disease that can be treated or prevented. Untreatable conditions, such as Alzheimer’s, are not looked for.
We provide expert advice and support in all aspects of DNA testing: paternity, maternity, siblingship, ancestry, DNA storage, and forensic consultancy. DDC has a large legal services client base and provides a comprehensive range of services which includes arrangement of sample collection, chain of custody, quality assurance, and assistance in the interpretation of results, backed by a dedicated customer support team and overseen by the company’s full time geneticist.

In fairness to 23andME, it leaves it up to the customer to unlock the more serious results – or not. When I unlock mine, I discover that, while I’m not genetically predisposed to such things as the BRAC1 or BRAC2 variant, Parkinson’s or MS, I have one of the variants for late-onset (mid-80s) Alzheimer’s. However, I don’t have any other markers for Alzheimer’s or family history or conditions associated with it or anything else listed in the rather lengthy disclaimer, which also stresses that it’s not a diagnostic result and to seek further advice from your GP if you are concerned.

In the case of a great-grandchild, or a great-great-grandchild, something even stranger can happen.  Remember that a child will get half of their mother’s DNA, but there is never ever guarantee which 50%.  The way it is chosen is fairly random, as far as scientists know.  Take the example of the 100% Eastern European person.  Their great-grandchild will inherit 50% of their DNA from their part-Eastern European parent, but there is a good chance that they won’t inherit all of the Eastern European DNA that they could potentially inherit.  It’s possible for a person to share NO DNA with a great-great grandparent, even though there is a verified genealogical relationship.
Hi Mark, can you tell me which test my mother in law would need to take, for me to find genealogical information on her paternal line? She never knew who her birth father was apart from the fact that he was an American serviceman stationed in England after WW1. She has no siblings. Is there a test suited for this? As she is nearing 100 years old, it would need to be a cheek swab test. Would it be beneficial to have my husband tested instead? Thanks.
Offering DNA test kits and a range of online subscription services, MyHeritage says that its database includes more ethnicities -- that's 42 -- than any other major testing service. The free 14-day trial will let you poke around the company's massive online database which includes 3.5 billion profiles in addition to information about over 100 million subscribers and their collective 46 million family trees. 

Because it is a genetic condition, FH is present at birth, meaning most people with this condition have high LDL cholesterol levels from a young age. Since many people with FH show no physical symptoms, this condition is typically diagnosed with a blood test for cholesterol. However, some people with FH may not be diagnosed until after experiencing symptoms related to early heart disease, including chest pain or heart attack.
The Y chromosome is a special chromosome, passed on from fathers to their sons, while mothers pass on mtDNA to both their sons and daughters. But mtDNA dies with men and so it survives only in the female line. This means that a man’s lineage can be followed along both paternal and maternal lines, while in a woman only her maternal or mtDNA line can be followed.