Hello.
The DMV-V form on e-Taxes expects a "Certificate of Joint Household" as a compulsory attachment in the case of the legal basis "Article 18 - families with three or more children", which no longer exists as of 1 January 2021. Instead, it could use existing resources at national level:
- Information on the applicant's children (shown in the e-administration),
- Application for extract of data on persons registered at the address or
- Application for a certificate of permanent residence.