I am seeing a lot of Not-the-Parent(s) Expected (NPEs) showing up. It’s becoming common as people who thought they could hide the secret before DNA testing became so cheap. While donors were promised anonymity in the 1970s and 1980s, it no longer applies. These days a second or third cousin can reveal an NPE. In addition a sibling may show as not being a full sibling. A parent may not show as being the parent. How people handle this depends on personal choice of the individual. Some will go DNA lies. In the case of close family – parent, child, half-sibling, aunt/uncle, niece/nephew, grandparent/grandchild, it tends to be fairly accurate. In some rare situations, it may be a bit off. Another exception is identical twins identified by DNA testing. If you have identical twins marry identical twins, it becomes hard to distinguish between them using a standard genealogical DNA test. It is possible to use specific tests that tend to be more expensive to figure out which twin is the parent of the child if it’s one case of identical twin parents. With both parents marrying another set of identical twins, it can still be done as there are minor differences between each identical twin. I covered the topic about differences in identical twins in this post – Identical twins aren’t all identical, study finds Atlanta Journal Constitution January 11, 2021 – Weirdness Wednesdays January 13, 2021
Most DNA companies give a range of possibilities with the exception of parent/child and sibling. Here’s an example from Pinterest – https://i.pinimg.com/originals/73/3f/12/733f128a098e0f8fb148de04b5eab10b.jpg. There are similar charts on different websites. Some use this chart; other use different charts. Here’s the ISOGG Wiki chart – https://isogg.org/w/images/thumb/c/c0/SharedcMProject20March2017.png/750px-SharedcMProject20March2017.png. The ISOGG Wiki chart gives an average and an expected range. In both charts, you can compare the ranges and see people can fall into different categories.
Previous DNA Saturdays posts: https://upsdownsfamilyhistory.wordpress.com/tag/DNA-Saturdays/