A family tree key is a reference chart or legend that explains the symbols, colors, lines, and abbreviations used in a family tree diagram, allowing anyone to read the relationships correctly. Without a key, a family tree is just a tangle of names and lines; with one, you can instantly tell a marriage from a sibling link, an adoption from a biological birth, and a generation gap from a direct descent.
Why Family Trees Need a Key
Most people first encounter family trees as simple drawings: grandparents at the top, parents in the middle, children at the bottom, all connected by straight lines. But professional genealogists and modern genealogy software use far more complex diagrams. A single chart can include dozens of individuals across five or more generations, with remarriages, half-siblings, adoptions, stillbirths, and unknown parentage. Without a standardized key, a reader might misinterpret a dashed line as a distant cousin rather than an adoption, or mistake a double horizontal line for a sibling bond instead of a marriage.
The key solves this by defining every visual element. It tells you that a solid vertical line means descent, a solid horizontal line means marriage, a dashed horizontal line means a partnership or unmarried parents, and a dashed vertical line means adoption or fosterage. It also explains the meaning of colors—for example, blue for males, pink for females, or yellow for a direct ancestor line—and the symbols used for dates, such as a cross for death or a star for a birth. In short, the key is the legend that turns a picture into a readable document.
Standard Symbols in a Family Tree Key
While no single universal standard exists, most genealogy software and published charts follow a common set of conventions. The following are the most widely used symbols and what they mean:
- Square – Represents a male individual in most Western charts.
- Circle – Represents a female individual.
- Triangle – Often used for a person of unknown or unspecified sex, or for a pregnancy.
- Solid horizontal line between two symbols – Indicates a marriage or a recognized union.
- Dashed horizontal line – Indicates a partnership without legal marriage, or a common-law relationship.
- Solid vertical line from a couple down to a child – Indicates biological descent.
- Dashed vertical line – Indicates adoption, fosterage, or a step-relationship.
- Double horizontal line (on a vertical descent) – In some charts, this marks a divorce or separation between the parents.
- Slash through a symbol – Often used to indicate that the person is deceased.
- Numbers or letters inside symbols – These correspond to a separate index or a notes section, not to the person’s birth order.
It is important to note that conventions vary. For example, some European charts use a circle for males and a square for females, the opposite of the American default. Always check the key provided with a specific chart before interpreting it.
How to Read a Family Tree Using the Key
Reading a family tree becomes straightforward once you understand the key. Start at the top—the oldest generation—and work downward. Each horizontal line connects two parents; each vertical line drops to their children. Siblings are shown side by side, usually in birth order from left to right. If a child has a dashed vertical line, the key tells you that the connection is not biological, so you know to look for adoption or step-parentage.
For example, consider a chart where John (square) and Mary (circle) are joined by a solid horizontal line. Below them, a solid vertical line leads to a square labeled “James.” Next to James, a dashed vertical line leads to a circle labeled “Emily.” The key tells you that James is John and Mary’s biological son, while Emily is adopted. If the chart also shows a dashed horizontal line from Mary to a separate square labeled “Robert,” with a solid vertical line down to Emily, you now know that Robert is Emily’s biological father, but Mary and Robert were not married. This kind of detail is impossible to glean without the key.
How to Choose or Create a Family Tree Key
If you are building your own family tree, you have two choices: use the built-in key from a genealogy software program, or create a custom key for a hand-drawn chart. For software like Ancestry, MyHeritage, or FamilySearch, the key is automatically generated and consistent across all charts. You do not need to create one, but you should learn what the program’s symbols mean, as they may differ slightly from the traditional manual.
For a hand-drawn or custom chart, create a key before you start drawing. List every symbol you plan to use, and define it clearly. For example:
- Square = male
- Circle = female
- Solid horizontal line = marriage
- Dashed horizontal line = unmarried partnership
- Solid vertical line = biological child
- Dashed vertical line = adopted child
- Slash = deceased
- Star = birth date unknown
Place the key in a corner of the chart, or on a separate sheet if the chart is large. Make sure the key uses the exact same symbols and colors as the chart itself.
Common Problems and Misconceptions
One of the most common mistakes beginners make is assuming that a family tree key is universal. In reality, symbols vary by region, software, and even individual family tradition. For example, some charts use a diamond for a stillborn child, while others use a small circle with a cross. A dashed line might mean engagement in one chart and divorce in another. Always rely on the specific key provided, not on memory.
Another misconception is that a family tree key explains the entire family history. It does not. The key only explains the visual language of the chart; it does not provide names, dates, or stories. Those are found in the accompanying notes, sources, or narrative reports. The key is a tool for reading the diagram, not a substitute for the data itself.
A third issue is the handling of unknown information. If a child’s parent is unknown, the chart might show a vertical line from a blank space, or a line from a single parent only. The key should specify how unknown parentage is indicated. If it does not, the chart is incomplete and potentially misleading.
Digital vs. Paper Family Tree Keys
With the shift to digital genealogy, the key has evolved. Online platforms like Ancestry and MyHeritage use interactive charts where you can hover over a symbol to see a tooltip explaining its meaning. This eliminates the need for a separate key, but it also means that if you export the chart as an image or PDF, the key may not be included. Always check the export settings to include a legend if you plan to share the chart with others.
Paper charts, on the other hand, always require a visible key. If you are printing a large family tree poster, place the key in a corner or at the bottom. Some genealogy software allows you to customize the key, adding your own symbols for specific events like military service or immigration. This is useful for specialized research, but it makes the key even more essential for anyone else reading the chart.
Costs and Tools for Family Tree Charts
Creating a family tree with a key is free if you do it by hand with paper and pencil. For digital tools, most genealogy websites offer free basic charts, but advanced features—such as custom symbols, large poster printing, or the ability to share interactive charts—often require a paid subscription. For example, Ancestry’s free account allows you to build a tree, but printing a large wall chart or exporting a high-resolution image may require a paid plan. Similarly, MyHeritage offers a free basic tree, but some chart styles and collaboration tools are behind a paywall.
If you want a completely free, open-source option, programs like Gramps (for Windows, Mac, and Linux) allow you to create detailed family trees with customizable keys and no subscription fees. The trade-off is a steeper learning curve and less polished output compared to commercial software.
Frequently Asked Questions
What does a dashed line mean on a family tree?
In most family tree keys, a dashed horizontal line indicates an unmarried partnership or a non-legal union, while a dashed vertical line indicates adoption or a step-relationship. However, some charts use dashed lines for engagement or divorce, so always check the specific key.
How do I show adoption on a family tree?
Adoption is typically shown with a dashed vertical line between the adoptive parent(s) and the child. Some charts use a solid line with a small “adopted” label, or a double horizontal line to indicate the adoptive relationship. The key should specify the exact method used.
What does a triangle mean in a family tree?
A triangle is often used for a person of unknown sex, or for a pregnancy that did not result in a live birth. In some charts, a triangle represents a stillborn child. Again, the key defines the exact meaning.
Can I use a family tree key for DNA matches?
No. A family tree key is for genealogical charts, not DNA matching. DNA testing companies use their own symbols and algorithms to show genetic relationships, such as percentages of shared DNA. Those are not the same as a family tree key.
Is there a standard international family tree key?
No. While many conventions are common, there is no official international standard. Different countries, software programs, and even individual families may use slightly different symbols. Always rely on the key provided with a specific chart.
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