How much house is in it?

Yes, the thing with daycare fees is of course true. The topic of children is something I don’t want to downplay either. But: even if 500€ daycare fees are added, we hopefully haven’t yet reached our maximum household income. My husband turned 30 last month, I turned 29 last month. We still have 30 years until retirement. Children are currently not planned. My husband has salary negotiations next year; as it currently looks, he will be promoted to senior (since 95% of the target achievement is already done). That will come with a higher salary. In the long term, we would of course like one of us to become self-employed (probably HIM) and the other to remain employed for security reasons (probably ME). And the daily rates in the SAP field are naturally considerable. But that is future music.

And that is exactly why I don’t want to calculate with that firmly, just as little as with children or inheritance or death or or or. We keep such things in the back of our minds and are well aware that there are more stressful and less stressful times in life. But I think we have pretty good cards for the future in an industry that will continue to grow. Therefore, I am currently calculating based on the present state and looking for things that could cost us dearly. And if I don’t find anything there, then I can move forward in 5- to 10-year steps and draw up scenarios.

To also strike a softer tone for once. In the current state, there is actually no problem, except that you are burning your money due to the high interest rates.

The problem lies in the target state with parental leave, part-time work, daycare, and so on, combined with today's expenses. You are currently spending 500€ more than we do with 2 children and have a 500€ higher installment. When this hits one part-time and one full-time salary, it gets tight.

Calculate this for yourself and write it down here. Feel free to do so over a period where 2 children are involved (without salary increases) + daycare + adjustment of living costs. That would be the worst case.

I’m curious...

That's all totally crazy.

It's perfectly fine if you're more the suspenders over belt type and hold your trousers up just to be safe, but to now diagnose everyone who doesn't share your future fears with mental confusion is a bit over the top.

What could possibly happen to the two in the worst case? Having to buy a used car? Going to a restaurant only once a week? Choosing between the Netflix and Sky subscriptions? Only getting every other generation of the iPhone?

I also get chills down my spine at the thought of having to live such a life in poverty, but two adults should be able to decide that for themselves, right?

It's perfectly fine if you're more the suspenders-and-belt type and want to hold your pants up just to be safe, but now accusing everyone who doesn't share your fears about the future of mental confusion is a bit over the top.

What could happen to those two in the worst case? Having to buy a used car? Going to a restaurant only once a week? Choosing between the Netflix and the Sky subscription? Getting a new iPhone only every other generation?

I also get chills down my spine when I imagine having to live such a life in poverty, but two adults should still be able to decide that for themselves, right?

Certainly nothing to those two! I already wrote that above. But when you have 2 children and can no longer work full-time (at least one), it gets interesting. The current situation has already been assessed by the OP in their first post.

What kind of poverty are you talking about?

You are spending €500 more today than we do with 2 children and have a €500 higher rate.

Now I’m slowly starting to understand where the problem lies.
Then I’m sorry, I probably tackled the breakdown of ongoing costs incorrectly.

I calculated the ongoing costs on the first page with an absolute buffer. We don’t spend that much more every month on “you want to afford something/miscellaneous”! Yes, you must be going crazy, who spends all that? This is a breakdown for our most extravagant times, basically what would remain in the worst case per month in the current actual state.
I also included the depreciation costs of the car and the coffee machine (as examples) in there (because you have to replace them at some point), to spread that out over the months in the long term. Vacations are included too, of course proportionally. I also rounded up fuel very generously, for example when we visit my boyfriend’s parents in Cologne, which doesn’t happen every month anyway.
Further down there is also what we would like to save per month in the worst case (€500 per person), and then I rounded the €3,700 down to €3,000 as the maximum to be taken (so that €700 would still be open per month with the current maximum spending behavior, also to have a buffer for new insurance due to the house construction — because I don’t yet know how expensive that will be).

We never, ever spend €500 a month on nonsense... We don’t have that many wishes :/
And of course it’s clear that we can spend much less from our nonsense budget above if tougher times come.
But I probably wouldn’t set food costs higher with 2 kids, since we are currently very careful not to throw anything away. Ergo, we almost always choose the more expensive small packages, mostly organic or from the farm. With children, one can also buy larger packages, which of course then calculate down per person.

But it gets interesting when you have 2 children and can no longer work full-time (at least one of you).

Why should you not be able to work full-time with 2 children can? Anyone who can and wants to afford this luxury simply has to make compromises elsewhere. In the end, it is just a matter of weighing individual priorities.