The 212 cM Match and an Adopted Grandfather
Your client's autosomal DNA results include a match, 'P.M.,' sharing 212 cM across 11 segments, predicted second-to-third cousin. P.M. does not match any known relatives on the client's paternal grandmother's line. Instead, P.M. matches a cluster of five testers, none of whom the client recognizes; that cluster shares no matches with the grandmother's line. The client's paternal grandfather, born in 1912, was adopted, and his birth parents are unknown. You have 20 hours and eight weeks. P.M. has agreed to answer one email but has not uploaded a tree.
1. Interpret the 212 cM match: what relationships are plausible, and what can and cannot be concluded from the amount of shared DNA alone?
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At 212 cM, the plausible relationships include second cousin, second cousin once removed, half-second cousin, and some first cousin twice removed or half-first cousin once removed scenarios. The amount alone cannot distinguish these, and it cannot prove a specific person. It does mean P.M. is a close relative, likely within the same generational range as the client's grandparents. Because P.M. does not match the known paternal grandmother's line and does match an unknown cluster, the strongest hypothesis is that P.M. is related through the unknown paternal grandfather, but that is an inference, not a conclusion.
2. Formulate a kinship hypothesis and a research plan to identify the grandfather. Explain how the shared-match cluster changes your approach.
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Hypothesis: P.M. descends from a sibling or cousin of the client's unknown paternal grandfather.
Plan:
- Ask P.M. for the one permitted email - request names of grandparents and great-grandparents and permission to share.
- Build a quick-and-dirty tree for P.M. and each of the five unknown-cluster matches using census and obituaries.
- Use the Leeds method to see whether the cluster resolves into subclusters.
- Look for a common couple in the 1900–1920 window in the grandfather's likely birthplace.
- Search adoption and court records for the grandfather's birth name.
- Triangulate with documentary records.
The unknown cluster is the key: it tells me to focus on the grandfather's line, not the grandmother's.
3. What ethical and practical steps would you take regarding contact with P.M. and the other matches?
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Ethically, I would contact P.M. through the testing company, explain the project, and ask only what P.M. is willing to share. I would not reveal the client's identity or the adoption without permission. I would get written consent before sharing P.M.'s information with the client, and I would avoid uploading anyone's data to public sites without consent. Practically, I would keep the one-email limit by preparing specific questions, and I would not promise P.M. a result. I would also tell the client that contact may yield no answer and that privacy laws may restrict adoption records.