In the olden days, when people got married a lot younger, there were probably lots of grandparents in their thirties

Still very common in the American South and probably other third world countries. Hasidic communities as well marry young and have lots of children.

'A lot younger' was usually still in their twenties, unless they were nobility getting married off for political reasons.

I know a man who became a grandfather at 34. He had a daughter at 16 and she had a kid at 18.

When I was a kid I had great great grandparents I visited. There were old people that talked about up to 4 generations of great, so great great great great grandparents were still alive. Yes, I'm originally from Alabama.

I had Great-Great Grandparents in my life until I was in my late teens because of this.

The average age of a groom in Britain in the 19th century was 27.

Men were generally unable to marry until they had obtained property.

And the average age was higher than the 20th century as well, because of the high infant mortality rate, it wasn't a "society of young people" at all.

Oh hell yes and they wasn’t that long ago. When I was 16 (1980s) I was friends with a girl also 16, whose mother was 31 and her grandmother was mid 40s. Both the mom and grandmom gave birth at 15/16.

As an aside They were cool as can be and most of my circle of friends would hangout at her house

I knew both of my Great Grandmothers, our family had a habit of starting early so to speak. One of them died when I was a teen from Alzheimer's and the one I was super close with and took for donuts and beer runs died the year I turned 21 just a couple of days after we went out for dinner, it was a soul crushing reality in how things can change without warning.

I once met a 32 year old lady holding her 1 year old grandson. She told me she had her daughter at 16 and her daughter had to out-do her and have her baby at 15. At the time, I was her age with my own small children...

On another note. I was close friends with a fellow who was the youngest of 10 kids from the same mother and 2 different fathers. Her first 8 kids were fathered by a man who died in the 1940's. She ended up with another man and had 2 more sons, one born in 1958 and then my friend in 1962. She was in her 50's when she had him! Unsurprisingly, my friend was orphaned by the age of 12 and ended up being raised by his older siblings along side nieces and nephews who were often times older than he was.

In my family the men tend to have children quite late in life. I'm nearing 40 and my grandfather was a Victorian (born 1897).

Life expectancy tended to be a lot lower, too. Once you lost your teeth, it was only matter of time. With no antibiotics, any injury that broke skin could be a death sentance, and over 30, 40 years, the odds stack up.

Childbirth was a pretty dangerous thing for women, too.

I know plenty of people who are grandparents in their 30s today.

My grandparents were married when 15. They ran away from home in California and settled down in Oklahoma where my family still resides

On my mom's side, my grandmother became a grandmother for the first time at 40. On the other hand, on my father's side, both grandparents were born in the 1880s.

My father and his first wife married at 17, had their first child at 18. She (i.e. that first child) had her first child at 17, who in turn had her first child at 18. My father thus became grandfather at 35, great-grandfather at 53; and I became uncle at about 7, great-uncle at about 25. Kinda cool tbh.