Have you ever wondered about those distant cousins you’ve heard whispers of — the ones who share a great-grandparent? Finding them can feel like searching for a needle in a haystack.
But these long-lost relatives hold valuable keys to your family history. This guide will equip you with the tools and insights to unlock the secrets of your second cousins, helping you piece together your lineage and connect with a broader network of kin.
» Uncover your family’s hidden branches with a DNA test
What is a second cousin?
Cousin relationships are based on how far apart two people are from their shared ancestor, which is often described in terms of “degrees of separation.”
- First Cousins: First cousins share grandparents. This means your siblings’ children and your children are first cousins to each other because they share the same grandparents.
- Second Cousins: Second cousins share great-grandparents. So, your grandparent’s siblings’ children are your second cousins.
Visualizing these relationships can be tricky. Using a family relationship chart, such as the one provided by MyHeritage, can be helpful. By placing family members within the chart, you can clearly see the connections that lead to second cousins and second cousins once removed.
» Read our in-depth guide on family relationships
Second cousin vs. first cousin once removed
- Second cousins share great-grandparents and are in the same generation as you. Think of it like your parent’s cousin’s child.
- First cousins once removed are either the child of your first cousin (younger generation) OR a first cousin of one of your parents (older generation). The “once removed” means there’s a one-generation difference.
Second cousins are on your same generational level, while first cousins once removed are a step above or below you on the family tree.
» Learn more about half and full relationships
How much DNA do second cousins share?
Second cousins typically share between 75 and 360 cM (centimorgans) of DNA, which is around 3.1%. Centimorgans measure the amount of DNA shared between relatives. Close relatives share more cM. For example, I share around 3,450 cM with both my mom and my son.
But I also see people in my DNA results who share 75-360 cM with me, but I don’t know how we’re related. Knowing we share DNA can guide my research to find our shared ancestor.
While DNA can vary slightly between individuals (about 0.1%), this doesn’t significantly impact the identification of second cousins. So, if your DNA results suggest a second-cousin relationship, it’s likely correct. By focusing on finding the common ancestor, you can usually confirm this relationship.
Second cousins in legal contexts
Second cousin relationships can have legal and social significance:
- Inheritance: Second cousins may be entitled to inheritances alongside you, as they share great-grandparents.
- Lineage societies: Proving a second-cousin relationship can help you and your family members gain membership in lineage societies like the Daughters of the American Revolution.
- Dual citizenship: In some cases, a proven second-cousin relationship may be used to support a claim for dual citizenship in another country.
Today, people are living longer, and many individuals have strong relationships with their great-grandparents. My parents, for example, have ten great-grandchildren, several of whom have close bonds with them. This increased longevity highlights the potential for these relationships to have a significant impact on individuals’ lives.
» Learn more about third cousins and how they fit into your family picture
Genetic implications of second cousin relationships
Concerns about the genetic implications of cousin marriages have long existed. Second cousins share approximately 3.1% of their DNA. While this level of shared DNA establishes a genuine genetic link, it’s important to understand the potential risks.
The National Institutes of Health (NIH) defines “consanguineous marriages” as those between individuals related as second cousins or closer. Children born from such unions may have a slightly increased risk of certain genetic disorders due to reduced genetic diversity.
Here are some potential risks:
- Increased risk of recessive genetic disorders: When closely related individuals have children, there’s a higher chance of both parents carrying the same recessive gene for a genetic disorder. This increases the likelihood of their child inheriting two copies of the gene, leading to the development of the disorder.
- Examples of potential risks: Some potential risks associated with consanguineous marriages include heart defects, lysosomal storage disorders, and an increased risk of stillbirth.
Important note: While studies have shown a higher prevalence of certain genetic disorders in children born to closely related parents, this does not definitively prove that consanguinity causes these disorders [1]. Many other factors can influence their occurrence.
» Confirm the paper trail to your second cousin using genetic triangulation
Second cousins and their role in medical advancements
Research and disease understanding
Identifying second cousins can provide valuable data for researchers studying hereditary diseases, genetic predispositions, and the impact of consanguinity (marriages between closely related individuals).
Research on offspring from consanguineous unions has made significant strides in identifying hereditary links to conditions such as congenital heart defects, neural tube defects, and developmental delays.
By studying these patterns, researchers can gain a deeper understanding of how genes are inherited and develop strategies for prevention and treatment.
» Learn more about second cousins once removed
Identifying potential organ/tissue donors
Knowing your second cousins can potentially expand the pool of potential organ and tissue donors.
Due to shared genetic material, second cousins may be more likely to be compatible donors for transplants than unrelated individuals. This can significantly improve the chances of finding suitable matches for those in need of life-saving transplants.
» Understand the difference between direct lineage and collateral relatives
Predictive medicine
Understanding your family’s genetic history, including relationships with second cousins, can help individuals make informed decisions about their health. This information can be used to identify potential genetic risks, allowing for early detection and preventative measures for certain diseases.
» Find out how shared ancestors might cause pedigree collapse
Overcoming challenges in identifying second cousins
Identifying and verifying second-cousin relationships can be a challenging but rewarding aspect of genealogical research.
Here are some challenges in identifying second cousins:
- Masking relationships: Other relationships, such as once or twice-removed cousins, can share similar DNA percentages and may mask a true second-cousin connection.
- Unfamiliar cousins: Researchers often encounter individuals identified as “cousins” in their DNA results, but determining their exact relationship within the family tree can be difficult.
Here’s how you can address these challenges:
- Visual mapping: Creating a visual chart of known cousin relationships can help identify potential second cousins and visualize their connections within the family tree.
- Verifying ancestral links: Once a potential second cousin is identified, it’s crucial to verify their connection to a known common ancestor. This process may uncover “non-parental events” in the family history, such as children born out of wedlock or previously unknown relatives.
- Gathering secondary evidence: Corroborating the relationship with secondary evidence, such as historical documents, census records, and family stories, strengthens the claim of a second-cousin relationship, particularly when non-parental events are suspected.
MyHeritage specializes in historical records and DNA testing and can be valuable in your quest to verify family relationships. You can use advanced search tools, community forums, and collaboration tools for family members to finally trace your lineage.
Significance of second cousin relationships
Understanding second cousin relationships offers a detailed perspective on family history, genetics, and societal dynamics. By carefully analyzing genealogical records, DNA data, and cultural contexts, we can unravel the intricate web of connections that bind us to our extended family.
Whether it’s navigating inheritance laws, exploring our genetic heritage, or simply deepening our understanding of our family’s past, recognizing and connecting with our second cousins can unlock a wealth of knowledge and enrich our lives in profound ways.
» Find your long-lost relatives with a DNA kit
