Kids

I once had the same FIRE SR of roughly 50% like you, and did the math on my situation and institutions and all that kids stuff, and we came to the conclusion (w. a GF income of half mine and roughly the same as yours but slightly higher COL than CZ) that each kid we had, would add 3 yrs to the FIRE goal, without any compromises that the kid* would care about or notice.

*: Kids when sub-6 dont give a crap about quality for example, food is food and a €1 sandwich or egg is just as good as anything else and even the cheapest clothing that will keep them warm/cold and comfy is just fine, so only institutional stuff and car seats and stuff like that actually have to cost a lot.