Visualizing Genealogical Relationships: Double Cousins

The best way to understand genealogy is to chart it. But few chart the past well because it is not a tree-form pyramid as everyone tries to use. Cousins married cousins, and that makes charting a different kind of craft.

Determined to learn the terminology for portraying the past, I researched relationship “sanguinity.” The charts I found are very difficult to understand visually, as well as the terms used to describe these relationships. There are many facts that influence chart construction:

• The true configuration is a diamond, not a pyramid. Generations do not double from the previous in numbers such as is presumed (2—4—8—16—32—64—128—256—512—1024—2048—4096—8192, etc.). If this were true, in ten generations back, there were 2,048 direct grandparents! But eventually, there are not enough people in the world to fill all these slots! There has to be a narrowing.

Forms of interfamily marriages are prior to 1900 (though a fuzzy line). Half the marriages were “reciprocal” (between families):

– cousin pairs
– sibling pairs
– intergenerational matches

• “Ancestor loss” is inevitable because grandparents do become shared between branches. People prior to the 1800s did not travel, so there were fewer choices for eligible matches. And to protect the valuables within families, marriages were arranged. Most people lived in small villages and surnames were rooted well to locations.

• Ancestor loss can be measured. Anyone who can trace relatives back to the 1600s will detect the dwindling of numbers, not only because records may be missing, but because of the inevitable shared ancestors. The average chart seems to show the dwindling of numbers around the 10th generation.

• Each chart is different. There are some “regular” configurations, but few family relations are even that simple! So the “irregular” configurations must be unraveled individually. Every chart has a different pace to occurrences.

The terms are complex. To describe relationships of extended family causes most people to roll their eyes as a result of its complexity. (I have “double first cousins fourth removed” in Germany) . People resort to just “cousins.” And when confronting these charting snags, most just throw up their hands and simply repeat names in more than one slot. Yet this does little to express the reality, as one person can’t be in two places at once.

• New configuration is needed. Linear relationships like tree branches used most often for Family Trees have to be abandoned for a lattice structure. The ancestor loss snags are the place where the chart begins the design—arranged more by relationship than by a specific family order.

Family charts are really more organic than linear. The configuration of sharing ancestors is most simply charted from:

Regular sibling pair—a brother/sister married a sister/brother. Their children are double first cousins.

Regular cousin pair—from first cousins (rare) to second cousins (more common) to third cousin pairings (most common), they can create complex charting very quickly! This illustration shows second cousin pairing. Notice how double first cousins have the genetic pattern of siblings.

double cousins chart design by Liane Sebastian-2

It is nice to think ancestors behaved in such an ordered way. However, they didn’t. There is no real “regular” configurations—there is something unique in each cluster. But I can’t look at family trees the same way anymore. They break apart pretty fast.. Instead, charting becomes a task of simplying the complex. Once configured, it is done, which is a relief. The past, presumably, does not change. Yet our relationship with it does.

Many family researchers come together when dissecting records from the 1600s. Go back further, and there are less people to chart. There is no beginning. But, if we had records from 100 generations, I wonder if ancestor loss balanced with new participants. We may never know because such records were not kept.

The pattern was broken with the generations that migrated in waves to Eastern Europe, Russia, North America, and South America. This reshuffles the genetic deck of cards! Today’s charts have little ancestor loss. But, anyone charting the past will confront these snags. And I think it is in these very oddities that stories are revealed. With dates, places, and the data about other family members, what happened to them does speak. To view these charts as too complex to understand glosses over the richness of the social fabric. With history as a backdrop, situations revealed, choices made are shown in the footprints left behind.

Please see these other pages about charting design:

Creating a Genealogical Chain

Unraveling a Genealogical Knot

Visual Interfamily Intermingles

Closer than Close: charting sibling to sibling relationship and ancestor loss


Liane Sebastian wears an editor’s hat, designer’s coat, and artist’s shoes.








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