A rough guide to how GEDCOM numbering works

Many people invent there own method of numbering indviduals when they embark on creating their family tree. As time goes by many discover their method is flawed as they add more individuals. It also becomes more complex as they start dealing with individuals who marry or have relationships with multiple partners. There is also the problem of dealing with inter-marriage which can produce duplicate individuals from the paternal and maternal lines of descent.

Back in 1995 the people at the LDS invented the numbering standard used in gedcom files. It is based on relational database design in which individuals and groups are added to a database in a random chronological order. In other words it is flexible and does not rely on a rigid chronological sequence of numbers e.g. I001, I002, I003. Nor does it use fixed generation numbers. Basically, it uses 2 tables, Individuals (e.g. I0030) and Family groups (e.g. F004). They also use a Notes number which is the same as the Individual number but the I is substituted by the letter N eg. I0100 and N0100. Additionally there is a Source ID (e.g. S001) which contains information about where you obtained the particular data e.g. General Records Office birth index.

Let's look at an expample of how this works:-

Now let's look at the ascendancy group he belongs to:

Now let's look at the descendancy group:

So what happens if you discover that they had an extra child e.g. a child in the middle of the sequnce between where 2 and 3 now are? The gedcom file needs to position this extra child (I0303) like so:-

Children: @I0201@ | @I0202@ | @I0303@ | @I203@ | @I204@ | @I205@

What happens if I0100's wife dies and he remarries? An extra group has to be created:-

So let's look at the numbering sequence for the children of individual I0100:-

In a way it is sequential but it does not have a simple running order e.g. 1, 2, 3, 4, 5, 6, 7, 8, 9 10, 11, 12.

The descendancy group for I0100 looks like this:

Descendancy: @F100@ | @F200@

If he has a 3rd wife then another group number is added. What if you discover that he had a relationship with another woman before he married his first wife (F405)? Then you add another group number like so:-

Descendancy: @F405@ | @F100@ | @F200@

If a couple marry but have no children then they still have a group ID.

The Ascendancy ID can be blank, as can the descendancy ID if an individual has no offspring.

So there we have it, a simple but flexible way of dealing with complex relationships.