A characteristic, talent, habit, or medical condition that runs in the family is one that is shared by multiple members of a family, passed down genetically or culturally across generations.
Also: Run in the family, runs in the blood
Grammar: “Runs” vs. “Run” in the Family
Whether you say runs or run depends on the grammatical number of the subject trait:
- Singular Nouns / Abstract Traits (Runs): Used with singular physical features, conditions, or abstract nouns (e.g., “Diabetes runs in the family,” | “Red hair runs in our family”).
- Plural Traits (Run): Used when referring to plural physical characteristics (e.g., “Big blue eyes run in their family,” | “Dimples run in my family”).
- The Idiomatic Reset (“It Runs…”): When summarizing a situation using the pronoun “it,” always use the singular verb: “We’re all stubborn. It runs in the family.”
“Runs in the Family” vs. “In One’s Blood” vs. “Runs in the Blood”
Because these idioms all reference biology, lineage, and inherited traits, they are frequently conflated. However, they emphasize different aspects of personality and genetics:
Runs in the Family / Runs in the Blood (Generational Patterns)
Runs in the blood is the older, historical ancestor of runs in the family. Both expressions focus squarely on generational recurrence; the fact that multiple ancestors, siblings, and descendants share the exact same physical feature, behavior, or ailment.
In One’s Blood (Inborn Passion or Talent)
While in one’s blood can be passed down from parents, it does not require a long family lineage. Instead, it describes an innate, deep-seated passion, instinct, or natural talent that defines who a person is:
- “She didn’t just learn to play the violin; music is simply in her blood.”
- “You can take him out of the mountains, but farming is in his blood.”
Origin & History: From Galen’s “Blood” to Modern Genetics
Today, we understand that traits are inherited through DNA and genes. However, ancient and medieval science believed that a person’s temperament, physical characteristics, and lineage were literally carried and passed along through blood.
“Runs in the Blood” (1600s)
The earlier variant, runs in the blood, first appeared in English print during the early 1600s. It stemmed from the classical humoral theory that physical constitutions and family temperaments flowed directly through the bloodstream.
“Runs in the Family” (Late 1700s)
By the second half of the 18th century, as the social concept of the nuclear family gained prominence in British literature, the phrase evolved into runs in the family. The verb run was used in its older sense of “flowing continuously like a river or current,” illustrating how a trait flows down the ancestral line from parent to child.
Sentence Examples
“Blonde hair runs in the family so no one can figure out why my brother has such dark hair!”
“High blood pressure runs in the family, so I make sure to exercise regularly.”
“Brown eyes run in our family, but I have green eyes.”
“Hard workers run in our family. We all start working as soon as we are old enough.”
“My grandfather loved woodworking, my father builds furniture, and now I build cabinets—it just runs in the blood.”
“We’re all crazy in my family. It runs in the blood. We’re from a long line of hell-raisers!”
Similar and Related Expressions
- Take After (Someone): To take after someone (an older relative) means to have a similar personality or character; to resemble an older family member or to behave like them.
- The Apple Doesn’t Fall Far From the Tree: A child closely resembles their parents in behavior, habits, or character.
- A Chip Off the Old Block: A child who looks or acts just like one of their parents.
- Cut From the Same Cloth: Sharing the exact same traits, values, or nature as someone else.
- Like Father, Like Son: Proverb noting the strong behavioral similarity between generations.
- Second Nature: A trait or habit so deeply ingrained that it feels natural and automatic.