My Gx2 grandmother was 36 and a widow with 3 children when my 22 year old Gx2 grandfather married her so I'd say anything is possible!
My mother left notes showing that her g-g-grandfather was one of three brothers born 1806-1811, which I thought was a small family for the time - maybe any girls were omitted. I can't find a trace of any siblings, and it seems the last child was born when the mother was 40, which makes sense. The husband was 10 years younger; when the wife died in her fifties he married another older woman, so he seemed to prefer it that way.
On the other side of my family I have g-grandparents from Ireland - he was born in 1821, she in 1810. I know of only one child, born in 1850. There may be all kinds of reasons for that.
At the opposite end of the scale, one of those three brothers married at 18; his wife was 19. To 20th-century eyes it looks like (was) a shotgun wedding, as a child appeared 6 months later. But I think that was fairly 'normal' behaviour as they would have been 'engaged'.
