The Surge of Double Last Names: A Shift in Family Dynamics

Two decades after the law allowing the transmission of both parents' surnames at birth, family habits in France are gradually changing. An Insee study released regarding births in 2025 indicates that 15.1% of newborns are now given the surnames of both parents. This shift is largely driven by evolving notions of partnership, the professional aspirations of mothers, and the recognition of same-sex families.

Persistence of Paternal Exclusivity in Birth Records

Despite the 2002 law that has enabled the combination of the father's and mother's names since 2005, traditional customs still hold significant sway. In 2025, nearly 78% of babies born in France received only their father's surname. Conversely, the percentage of children bearing solely their mother's name stands at just 6.8%, predominantly occurring when the father has not acknowledged the child at birth.

The rise of double surnames is evident, however. In 2014, only 10.3% of infants received both surnames, which has increased to 15.1% in 2026, marking an almost five-point rise over eleven years. When parents opt for a double surname, a sociological trend emerges: in three out of four cases, the father's name is listed first. This preference is partly due to the legal framework that defaults to the paternal surname unless otherwise specified by married parents or in cases where the father acknowledges the child from birth.

Changing Family Structures and Mothers' Careers

Contemporary family models play a crucial role in this transformation. Among unmarried parents, the dual surname transmission applies to 21.7% of births, with this figure rising to 23.1% when the couple does not cohabit. For these mothers, adopting their surname alongside the father's is an essential means of establishing a legal and social connection with their child.

The professional background and age of the mother also significantly influence this choice. The incidence of double surnames notably increases among mothers aged 40 and older, reaching 20.5%. When these mothers hold scientific, artistic, or senior public sector roles, over 31% choose to pass on their surname alongside the father's. Having established a recognized professional identity before motherhood, these women are more inclined to carry their surname into the next generation.

Interestingly, the age gap within couples sheds light on attitudes toward equality. When the father is younger than the mother, 20.6% of children receive both surnames, a proportion that gradually declines as the father's age increases.

The Impact of Same-Sex Parenting and Cultural Roots

For female couples, the practice of assigning double surnames has become a significant norm, both practically and symbolically. Nearly 60% of children born to lesbian couples carry the surnames of both mothers. This trend has been facilitated by the 2021 bioethics law and the option for joint anticipatory declaration, ensuring immediate and equal legal recognition for the non-birthing mother. In cases where no formal choice is made, the civil registry automatically assigns both names.

Cultural traditions and regional origins also bolster this trend. The South-West of France stands out with a strong maternal surname transmission tradition, particularly in the Pyrénées-Atlantiques, where nearly 27% of children bear a double surname, followed closely by the Landes and Pyrénées-Orientales. On an international scale, families with roots in Spanish or Portuguese-speaking countries predominantly maintain the double surname tradition, with this custom observed in more than half of their children.