Requirements for child construction allowance: primary vs. secondary residence

Hello everyone,
we plan to buy an (existing) house in the next few months and move in with our children (before 12/31/2020). That means we meet (in addition to income etc.) the requirements for the Baukindergeld. Now we are wondering what impact it has on the funding criteria if we do not use the house permanently as our primary residence for the next 10 years, but (due to work) change our main residence, while continuing to use the purchased property as a secondary residence ourselves during this time. In my opinion, it is not quite clear from the KfW funding criteria catalog how this constellation affects the funding criteria. Does anyone here in the forum perhaps have advice?

It will no longer be checked ... it’s not such a bureaucracy monster after all

Is only checked once at the time of application, iirc it also says so on the KFW site.

Does that mean the main residence only has to be there at the time of application and later it doesn't matter? I only called the KfW this week, and they clearly said BKG only if the children's main residence is there. I have the problem that the father of my children and I live separately and for historical reasons (we used to live in his house) the children are still registered there. He does not agree to a change of the main residence registration. According to the current situation, I will lose the BKG because of that. Only if I were allowed to register the children with me and half a year later we register them back... (that's important to him)... that might be a solution I could offer him?

Does that mean the primary residence only has to be there at the time of application and later it doesn't matter? I just called the KfW this week, and they clearly said BKG only if the children's primary residence is there. I have the problem that the father of my children and I live separately, and for historical reasons (we used to live in his house) the children are still registered there. He does not agree to a change of the primary residence. According to the current situation, I will lose the BKG because of this. Only if I were allowed to register the children with me and six months later we register them back... (that is important to him)... that might be a solution I could offer him?

Sure, you can do it like that. But please keep in mind that in many municipalities, deregistration also affects entitlement to a daycare place, etc. Unfortunately, a lot depends on the registration in Germany. Where do the children live? I read it as if the children live with you? Or with your ex?

Fortunately, we live in the same city, and we share the care of the children, about four days a week with me and three with him. So they live with both of us, but there can only be one main residence...