MMM sells shovels in a goldrush, and got divorced (with relatively young kids) out the blue while selling his white picket fence (albeit a cheap one) lifestyle dream for years. Hardly the one to bring up as an example for a successful FIREee.

I wouldn't go as far as say they're incompatible; I'm sure it's doable. But there's a pretty big difference in believability between the claim that "engineers are much more likely to be FIRE people, to the extent it makes a noticeable difference in the engineering job market, now of all times" vs "FIRE people w/ kids exist, but are outliers among outliers"

Ok, that seems reasonable. I got stuck on "there's plenty of engineers who have kids (hence, very much not FIRE)," which seems like an oversimplification of your views.