The Kekule number, also known as the Sosa-Stradonitz numbering system or Sosa number[1]for short, refers to the number of a person in a genealogical list or pedigree according to Stephan Kekule von Stradonitz. This numbering system, which has established itself internationally, was used as early as 1590 by Michael von Aitzing, then in 1676 by Hieronymus de Sosa and in 1883 by Francis Galton.
Regardless of gender, the test person receives the number 1, their father the number 2 and their mother the number 3. If a person has the number n (e.g. 2 for the father), then their father receives the number 2-n (i.e. doubling and thus the number 4 for the test person's paternal grandfather), the mother 2-n + 1 (i.e. 5 in this case). The father of 10 receives the number 20, the mother receives the number 21.
All male ancestors therefore have even numbers, all female ancestors have odd numbers.
The proband and the ancestor generations I to IV are therefore assigned the following numbers:
