Surname List | Pedigree Chart
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They're simple, really. Every person in a family tree has a number, N, starting with 1 for the root person (usually yourself, but it my case it's my kids). Their father's number is 2N, their mother's is 2N+1, and their descendant's is INT(N/2).
Excepting the root person, the generation they're in is INT(SQR(N))+1, and men always have even numbers while women have odd numbers. For the root person (1), these things don't apply.