Suppose that married persons X and Y are moving to Germany. They will share a Hauptwohnung (primary residence) in city A, but X will additionally occupy a Nebenwohnung (secondary residence) in city B because X has a job at the other end of the country. So far so good: both will register as Hauptwohnung in city A, and X will additionally register as Nebenwohnung in city B.
However, due to timing reasons, X is moving to Germany before Y does, and will live primarily in what will be the Nebenwohnung for the first 6 weeks or so. Can X register their residency in city B as Nebenwohnung, before X and Y together register their residency in city A as Hauptwohnung? Or must X initially register residency as city B as Hauptwohnung, and then re-register in city B as Nebenwohnung as soon as Y moves to Germany and both partners register together in city A as Hauptwohnnung?
The registration form (example from Offenbach, but I expect it's the same elsewhere) appears not to ask people registering a Nebenwohnung, what their Hauptwohnung is, although it does ask for address details for the Ehegatte (partner).