If that were the case, then the demographics data would not show a major shift. It would just bias of a relatively small group. However, demographic data clear

If that were the case, then the demographics data would not show a major shift. It would just bias of a relatively small group. However, demographic data clearly shows a trend over the past several decades. Look up "Mean Age of New Mother" statistics. E.g. here's data from the US: https://www.cdc.gov/nchs/data/databriefs/db232.pdf https://www.cdc.gov/nchs/data/databriefs/db232.pdf It's more dramatic if you extend the data back to the 70's. You can see the same trend in most countries. On average, people are having their first children at a significantly older age than a couple of generations ago. That doesn't mean that folks _aren't_ having children early at all. E.g. I have _tons_ of friends that had kids as teenagers (and a lot at 14, too) and were already grandparents years ago in their 30's. But that's not representative of the overall population. This means that children knowing their great grandparents really is becoming more rare today than it was 30 or 40 years ago.