Floor plan of a two-family house with a stepped floor - too compact?

And what happens to the children's floor when you move into the (small) ground floor apartment? I had read something about renting it out, but that is probably easier said than done, isn't it?

While reading, I thought: well, even if adults don’t like slants, you can still give the kids nice rooms under the roof. But then I also thought that the roof terrace does make some sense if you live on the upper floor and give the garden to the seniors.

We will not completely forgo the garden; the garden will be divided – the parents get the small piece in the south and we get the slightly larger piece in the south and west.

But I only see the roof terrace for the kids. I don’t know if people actually use it like that. Also the gallery… that is a cozy area for the kids, but a restricted zone for adults ;)

..for that we still have a balcony on the upper floor:-)

To put it in order, (aside from the floor plan): you give up a larger footprint so that some garden remains, but then you don’t really have anything from the garden, or rather, the remaining garden piece now has to be maintained by the seniors.
Does that make sense? Basically it will be a two-family house and remain a two-family house. A bit of garden share for some parking spaces and that’s it.
Then it is assumed that the 30-year-olds have the same living needs as the over-70 seniors.
The seniors’ apartment is nice, but I find the 8-seater dining table somewhat out of place and too large. The bedroom is a bit too cramped. A small dining table makes sense near the kitchen. Guests can be accommodated more cheaply and with more privacy in a hotel. Later on, the partition wall of the bedroom could be removed…

But: I’ll throw another suggestion into the room:
Increase the footprint after all, put a living kitchen, WC and utility room on the ground floor for the young family, then adapt the upper floor on that footprint with a small living room and children’s room. Probably the bedroom will also fit there.
Just as an example in sketch form (without binding measurements or anything, just as an approximate size)

Very interesting idea – we had also toyed with something like that. But unfortunately the house became too wide for us as a result. It was even cheaper.

..there is also about €65K in funding on top, which I forgot to add.

And where do those come from, if I may ask? Apart from that, I would say that even including this hidden reserve for the wishes/requirements (Kfw 40), geothermal energy, ... the budget will be tight, aside from the fact that a €30K buffer (additional costs?) also seems too little.

And what happens then to the children's floor when you move into the (small) ground floor apartment? I read something about renting it out, but that’s probably easier said than done, right?

Yes exactly, we wanted to rent it out later. Either to one of the 3 children or to someone else. The stairwell is designed so that you can go directly from the house entrance through the stairwell to the top floor. We now wanted to have connections for kitchen etc. installed so that the apartment can be used separately later. Whether it will be easy or difficult to rent out the apartment, we can’t say for sure yet. But such "penthouse apartments" with terraces facing south are actually always very popular :-)

And where do they come from, if I may ask? Apart from that, I would argue that even including this hidden reserve in the wishes/requirements (KfW 40), geothermal energy, ... the budget will be tight, regardless of the fact that a 30 K buffer (additional costs?) also seems too little.

The approx. 65K € (75,000€ - minus approx. costs for the energy consultant) is the subsidy we will receive as a grant after the completion of the house.

That could be

Either one of the 3 children

That could then only be the youngest child, since the apartment is not available before, so ... in 20 years? No idea how your scheduling looks, but there are indeed some dependencies.