“My husband is French so the children are automatically French. We got them French ID cards because they are free and Britsh passports are expensive. The youngest has a French passport too because the prefecture made a mess of her ID application.”

 

Neither parent is French (or born in France)

The law on children born in France to foreign parents keeps changing.

 

At the moment the law is that a child born to foreign parents can't have French nationality unless the state its parents come from refuses to give its own nationality to people born outside the borders.

 

Once he/she is 18 then he can apply for French nationality on the grounds of having been born in France but he must have lived in France for the last five years. It's possible to do an advance request. At 16 without parental permission and at 13 if both the child and the parents agree on asking. You still have to fulfil the 5 year residence criterium.

Children born in France have the right to French nationality. They don’t do a “demande” but a “déclaration”. If they fulfil the residency requirements (and they haven’t got a criminal record) then French nationality can’t be refused.

http://www.justice.gouv.fr/publicat/gnationa.htm

 

Can my baby have dual nationality?

This depends on the agreements signed between France and your country or origin. Some countries won’t allow their citizens to have another nationality.

British citizens can have both nationalities.  In France they will be considered completely French (they can’t ask the British embassy for help) and vice versa in the UK.