Generation Difference

Not to be confused with Genetic Distance, the Generation Difference is a measure of how many parents (or steps of ancestors) separate two people from a common ancestor. The number of ancestors (or steps) is often reported as a value in Autosomal match comparisons between two people, and even by GEDCom tools telling how two people are related. If the number of steps to the common ancestor is the same, the generation difference is simply reported as that number. If the number of steps is different, the generation difference can be reported as an average of the two counts. Often, genetic genealogy tools calculate a value based on a heuristic from looking at the DNA matching content. We use the Generation Difference to figure out the relationship between two individuals that are Cousins; that is, share common ancestors.

Note that this is different then the measure of Consanguinity (or degree of kinship) which is measuring the total number of meiosis steps between each individual. Which is the sum of the two counts of steps from each person up to a common ancestor. Note the word sum versus difference. Similar terms but reporting on different things. Each handles issues of half as opposed to full relations differently as well.