BG Bau construction project rental apartment

Hello everyone,
I have a somewhat unusual situation and would appreciate support.

I live with my wife and child as well as my wife’s widowed uncle in a two-family house, which belongs to my wife’s uncle. We are tenants in the property and assist with everyday matters and property maintenance.
We would like to realize an extension for a children's room; the building application has already been approved.
The BG Bau has registered my uncle as the builder, since the property is solely in his name, to insure the workers. However, everything is carried out by us and specialist companies.
Is it possible to have us named as builders by the BG Bau as well, so that we do not have to insure ourselves as helpers? Or is everything always seen from the perspective of the uncle, because he is officially the builder but not involved in the project at all?

Thank you and best regards

because he is officially the builder,

It is his house and therefore also his extension and thus his project. You are and remain only a helper