and there are restrictions that prevent the adoption of “stepchildren” by one parent.

That one was judged unconstitutional in Germany as it bereaves the child of a perfectly suitable caregiver – that is it wasn’t a matter of gay rights for the court but children’s rights. In the end, before gay marriage was introduced, the only difference between marriages and civil unions was that gay couples could not adopt jointly, only one after the other, and generally speaking authorities are quite reluctant when it comes to singles adopting kids they aren’t related to by blood.