Genealogy Collateral and Cluster Research

What are Collateral and Cluster Research

  • Ancestors descend directly: your parents, grandparents, great-grandparents, etc. Direct line ancestors are those shown on a Pedigree chart.
  • Collateral Ancestors are not the direct line ancestors, but who share a common ancestor with you. Collateral relatives would extend to include aunts & uncles, great-aunts & uncles, nieces, nephews, and cousins.  Researching collateral lines means conducting research on the surnames who married into your surname of interest: in-laws, aunts and uncles by marriage, sisters-in-law, brothers-in-law, additional spouses of ancestors along with any stepchildren, nieces, nephews and cousins, etc.
  • Cluster Research would be searching within an entire geographic area, or group of records, or known associates of your ancestor. Looking for clues about people, places, historical happenings, or other connections that may not involve your direct ancestors but can illuminate their lifestyles.

    This work is especially important when dealing with common names and can help validate questionable sources. This is a technique employed by genealogists to learn more about an ancestor by examining records left by the ancestors cluster. A person’s cluster consists of the extended family, friends, neighbors, and other associates such as business partners. Researching the lives of an ancestor’s cluster leads to a more complete and more accurate picture of the ancestor’s life.

    Cluster genealogy is most often used to break through a  “brick wall”, to build a genealogical proof, and/or to develop context for an ancestor’s life.

    When you research the Friends, Associates and Neighbors (F.A.N. club) who were part of the community of your direct line ancestors, this usually means focusing on the geographical area. A few great resources for finding FANs:

    • US and State Census dRecords. When you look at the neighbors, you may be able to learn something. I see many familiar names in my ancestors census records. I’ve found my grandmothers sister living with one of the neighbors as a servant.
    • If you find your ancestors on Plat Maps, you can see who their neighbors were (See my post of Plat Maps for more information)..
    • Baptism and Marriage records will usually list witnesses. Who were they? What connection did they have to your family?


Both Collateral and Cluster research are typically missed because they can be time-consuming and we tend to focus on the direct line.  Both are back door approaches and can be considered fishing expeditions that are too time consuming, but Cluster research can be very helpful when trying to break down those brick walls or when you have a common name ancestor. Quick Lesson 11: Identify Problems & the FAN Principle 1 by Elizabeth Shown Mills, provides great examples. You may just find a clue that will break down that brick wall or enhance your ancestors story.

Best Practices for Cluster and Collateral Searching:

  • Always usse a research log.
  • Formulate theories and write them down.
  • Try spelling variations on the names.
  • Stop relying on records that are indexed.
  • Try swapping given and middle names.
  • Search by address.
  • Do a reasonably exhaustive search.
  • Search over township, county and/or state boundaries.
  1. Elizabeth Shown Mills, “QuickLesson 11: Identity Problems & the FAN Principle,” Evidence Explained: Historical Analysis, Citation & Source Usage ( : accessed 04 Mar 2015)

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