I’m one of 4 kids, and I’m the only one who has had DC of my own (two).
Brother 1 (45) never really wanted them, ended up marrying someone who already had a child, they thought about having one together but she’s now infertile because of endo, they’re not too bothered as they like their lifestyle as it is.
Brother 2 (39) very shy and socially awkward, only ever had one gf and that was years ago, he seems to prefer cars and cats.
Brother 3 (32) was always very clear that he never wanted children and is now in a LTR with a 45 year old woman who has grown up children, so can’t see it happening.
So if you think that if you go by the old 2.4 children theory, there would have been 8 or 9 children in my family, and there’s just 2.