How to Find Twins on Pedigree Charts

A pedigree chart is similar to a family tree in that it breaks down family relationships over several generations. The chart shows things like marriages and children in a family through the generations. Special symbols and ways of connecting the different members of the family help you learn more about them, including finding twins or other multiples. You can learn several details about the twins once you understand the basics of pedigree charts.

How Pedigree Charts Help

Pedigree charts track genetic information from your family. Depending on how detailed the chart is, it can also provide medical information about your relatives. You can learn more about diseases that run in the family, for example. Identifying twins on a pedigree chart may help you see if they run in your family, which can be helpful for your own family planning.

Basics of Pedigree Charts

Before you figure out the symbols that represent twins, it's helpful to have a basic understanding of symbols and connections used on pedigree charts. Males are represented by squares while females show up as circles on the chart. Parents appear side-by-side above their kids with a horizontal line connecting them to show their marriage.

A single vertical line extends down from that connection line to lead to the children of the couple. If the couple has only one child, that child's gender symbol appears at the end of the vertical line. If the couple has more than one child, you'll see another horizontal line at the end of the vertical line. Below that horizontal line, you'll see a vertical line for each child leading to that child's gender symbol.

How Twins Are Represented

Twins appear below their parents just like all other kids. However, instead of each having a single vertical line leading down to the gender symbol, you'll see two diagonal lines that start from the same spot on the horizontal line. That shared starting point shows that the two kids are twins. The twins' gender symbols appear at the bottoms of the diagonal lines. Once you spot the diagonal lines, you can tell if the twins were boys, girls or one of each based on the symbol displayed.

You can also tell whether the twins are fraternal or identical based on the chart. One obvious indicator of fraternal twins would be one male and one female twin since identical twins always have the same gender. However, you can have two boys as fraternal twins or two girls as fraternal twins, so you shouldn't assume they're identical just because they're the same gender. If twins are identical, you should see a horizontal line connecting the two diagonal lines that lead down to the gender symbols. Some pedigree charts instead display a horizontal line connecting the two gender symbols to create a triangle shape. For fraternal twins, you won't see any extra lines connecting the diagonal lines.

The pedigree chart may provide additional information about the twins you find. A diagonal line through the gender symbol indicates that the person is no longer alive, so you can tell if the twins in your family are still living. Detailed charts may also include health information under the twins, which lets you see if they had any medical issues.