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.

Download CommonBiologicalAncestor-V1.1.zip

• 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, translation source files, and a ready-to-use Danish translation in locale/da/LC_MESSAGES/addon.mo.

1. Close Gramps.
2. Extract the ZIP archive.
3. Create a folder such as CommonBiologicalAncestor in the Gramps user plugin folder.
4. Copy hascommonbiologicalancestor.py and hascommonbiologicalancestor.gpr.py into that folder.
5. Restart Gramps. Loading errors can be checked under Help → Plugin Manager.

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.