French citizenship by descent: parents, grandparents, and the family chain
Learn why a French ancestor is only the starting point and how to test nationality and legal parentage at every birth.
Can French nationality pass through your family?
Possibly. Ask first: was your legal parent French when you were born? If the French person was a grandparent or earlier ancestor, repeat that question at every earlier birth.
Article 18 of the Civil Code states that a child with at least one French parent is French. That short rule does not let you skip an intermediate generation.
Use two questions for every handoff
Keep parentage and nationality separate:
- Who was the legal parent, and when did that filiation become effective?
- Was that parent French on the child's birth date?
Article 20-1 says filiation affects nationality only if established during minority. France changed civil majority from 21 to 18 effective 7 July 1974. Historical cases need the law and transitional rules then in force, not a mechanical age-18 test.
Start with yourself and work backward
Create one row per person:
| Person | Decisive date | Parentage proof | French status proof | Open issue |
|---|---|---|---|---|
| You | Your birth | Full birth act and any acknowledgment or judgment | Parent's status on that date | Missing or conflicting record |
| Parent | Parent's birth | Link to grandparent | Status of grandparent then | Loss, late filiation, territory |
| Earlier ancestor | Next child's birth | Link to that child | CNF, judgment, decree, declaration, or other route evidence | Historical rule |
A birth act usually proves civil-status facts. A passport can show official treatment as French at a date. Neither necessarily proves the full chain. Read what French records prove.
What can interrupt or complicate the chain?
Manual review is essential when the record includes:
- foreign naturalization, renunciation, or another possible loss event
- a birth or parentage event under older sex, marriage, legitimacy, or acknowledgment rules
- parentage established late, a foreign judgment, adoption, kafala, PMA, or surrogacy
- a former French territory
- long residence abroad and the separate Article 30-3 facts
- conflicting identities, reconstructed acts, a prior refusal, or a deadline
Unknown is not no. Mark the missing fact and find the record that could answer it.
Is the next process a CNF?
Maybe. A certificat de nationalité française, or CNF, proves existing French nationality. It does not create it. Review the CNF guide after mapping the chain.
A declaration, reintegration, or naturalization is different. Article 21-12 may cover certain children in simple adoption or care situations. Articles 21-13 and 21-14 have narrow possession or remedial routes. Spouse, ascendant, and sibling declarations have their own current conditions. Reintegration is personal to someone who was French and lost that status. None is a generic ancestry grant.
What should you do next?
Write down the exact birth date for every handoff. Next to it, identify the record that proves the parent's legal status and the record that proves timely filiation. Do not pay for apostilles or translations until you know which documents the process needs.
A French court or competent authority decides status or acquisition. ByLineage is private and may match a case with an independent specialist.
Sources checked: 27 August 2026. Historical conclusions require the version of the law in force on each event date.