H @Jj061987i
The father must give his consent for your child to do the Einbürgerung. I have looked into this question and have not found any specific law or administrative guideline where it states that both parents with shared custody must be present when submitting the application or when the child is granted German citizenship.
The father will certainly have to co-sign the child’s application form for citizenship with you.
If he cannot attend the immigration office in person, then he must in addition give his written consent to the Einbürgerung.
The office in Berlin, for example, does not mention anything about the presence of both parents, only that the other parent with custody must provide their consent:
„Für Kinder unter 16 Jahren mit gemeinsamen Sorgerecht der Eltern: Einverständniserklärung des anderen sorgeberechtigten Elternteils“
They also provide a sample form (Muster: Einverständniserklärung des anderen Sorgeberechtigten) which the parent fills out, signs and submits with a copy of their signature as it appears on their ID:
https://service.berlin.de/dienstleistung/318998/
The authorities may require him to have this document notarised. This means that the father must sign it in the presence of a notary. The notary checks his identity and give an official seal confirming that he did indeed sign it. The authorities in Berlin do not mentioned requiring this but it is generally required in important administrative matters to be absolutely sure of the identity of the person who signs a document. This type of notarisation is called ‘offizielle Bglubigung’.
There is another type called ‘amtliche Beglaubigung’ which can be done at the father’s local Bürgeramt/ Rathaus (the office for local administrative tasks such as doing an Anmeldung) if he lives in Germany. This is cheaper than going to a notary and in my view is also sufficient to present to a German authority in this case.
There is no reason to apply for Alleinige Sorgerecht with regard to citizenship. It is not a requirement for citizenship, only the father’s consent is a requirement. How you decide on custody arrangements is a family matter and not something that an immigration officer should be pressuring you about. If the officer persists in this, request the legal basis (gesetzliche Grundlage) for it.
Best,
Éanna