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Several instances have come up recently in which people have identified unfortunate cases of incest in their families. Some of these cases involve a woman having a child with a brother or uncle.

The first thing I like to ask someone when they discover that there’s incest in their family is if they feel they need to talk to a counselor. People shouldn’t have to navigate those feelings on their own if they don’t want to. This great blog post has a link that you can follow to get in touch with a counselor. (I also have an article about how you can further add to the calculation provided at the linked blog post.) I believe that the contact information above may be the same as what’s provided in the ‘Are Your Parents Related Tool?’ at GEDmatch.com. I’ve always thought that this was a link to a counselor counselor, but I recently learned that it may only be a way to contact genetic genealogists who have experience with cases like this. While this is helpful, I believe that there should be a second link to a traditional counselor in the event that a person wants credentialed support emotionally, and not just help navigating genetic genealogy. 

After talking to a counselor, people are likely going to look for answers. On top of knowing that, for example, your parents are closely related, imagine the pain of not knowing how they’re related.

I find myself in the position of having a highly accurate model that can calculate the likelihood of different relationships. In order to help more people than the ones I’ve worked with, and to help people find answers more quickly, I’m going to start providing some statistics that I’ve already calculated, just as I do with my other models.

If you are here because incest in your own family, I do hope that you’ve already gotten any emotional support that you need. If not, I hope that you speak to one before reading further. I may decide to take these results down eventually if I can manage to get them into the hands of counselors or other genetic genealogy professionals who handle such cases.

Figure 1. Statistics for comparison of one’s own genome to itself, such as can be done with the Are Your Parent’s Related tool at GEDmatch.com.

If you have discovered that your father is actually a close relative of your mother, you may not be able to tell exactly how they’re related by looking at the regions over which your chromosomes copies are identical. If your father is your mother’s brother or her son, the averages of those values are the same: You would expect to have about a quarter of your segments identical to each other. However, if you know that one of the two options is the case, Figure 1 could assist you if your identical regions add up to less than 9.3% or more than 45% of your genome. In those cases, and even for values that are several percentage points further towards the inside of that range, you could deduce that your father is not also your maternal uncle–it would be the case listed ‘brother’ instead.

Figure 2. Shared percentages for your 1C1R, whose father’s parents are your maternal uncle and that uncle’s close relative listed in each row. Each simulation consists of 500k trials, which is important for understanding the minimum and maximum values listed.