Common Biological Ancestor

Common Biological Ancestor is a custom Gramps filter rule that finds people who share a biological ancestor with a selected person.

Unlike Gramps’ built-in common-ancestor rule, it follows a parent link only when the child relationship is recorded as Birth . Adopted, foster, step and sponsored-child relationships are therefore not treated as biological connections unless a birth relationship is also recorded.

What “biological” means here. Gramps records each child’s link to a parent with a child-reference type — Birth , Adopted, Foster, Stepchild or Sponsored — shown in the relationship drop-down on the child reference. This rule treats only Birth links as biological and follows those alone. Wherever this page says biological, it means “connected through a Birth child-reference”. Gramps’ own term for the link is Birth; this addon calls the resulting line biological because that is what the traversal captures.

Source & Downloads

• Designed for Gramps 5.2 or later.
• Tested on Gramps 6.0.8 with Windows 11 and Zorin OS 18.1 Core.
• The package contains the two rule files, README.md , LICENSE , translation source files, and a ready-to-use Danish translation in locale/da/LC_MESSAGES/addon.mo .

1. Close Gramps.
2. Extract the downloaded ZIP archive.
3. Copy or extract the project folder into your Gramps user plugin folder.
   Keep the complete folder structure unchanged, including any `locale` folder included with the project.
   
   The user plugin folder is normally located here:
   
   - **Windows:** `%AppData%\gramps\gramps(version)\plugins\`
   - **Linux:** `~/.gramps/gramps(version)/plugins/`
   - **macOS:** `~/Library/Application Support/gramps/gramps(version)/plugins/`
   
   Replace `(version)` with the Gramps version folder used on your system.
   Start Gramps again.
4. Check that the installed filter, rule, gramplet or tool is available where described in the project documentation.
   
   If the project does not appear or fails to load, check **Help → Plugin Manager** for an error message.

1. Close Gramps.
2. Delete the project folder that you added to the Gramps user plugin folder.
3. Start Gramps again.
   
   Because the project was installed only in the user plugin folder, removing that folder removes the test installation without changing the original Gramps program files.

1. Open Edit → Person Filter Editor .
2. Create or edit a person filter and add a rule.
3. Under Ancestral filters , choose People with a common biological ancestor with <person> .
4. Enter the reference person’s Gramps ID and save the filter.

The resulting filter can be used for reports, exports and tags, including ProfileTag and the GEDCOM filter .

The result depends entirely on the child relationship type stored for each parent. An adopted or foster child left at the default Birth relationship will still be treated as biological.

Use Non-Birth Child Relation to review people who are explicitly recorded with a non-birth relationship.