Most made it above 40.
If you look at the English monarchs who lived past 20 years old:
- 91% made it to 30
- 80% made it to 40
- 54% made it to 50
- 33% made it to 60
Obviously people live longer now. Males can expect about 2 decades more of life now, and survivorship doesn't start dropping at a noticeable rate until 55 due to a lack of wars, plagues, etc.
Also, marrying early only applied to females. With some exceptions for arranged marriages in royal lines, most male nobles got married in their mid-late 20s after they had an opportunity to accomplish something in their life and provide for a family. Girls were typically married in their mid-late teens.
If we are talking about regular people, age of marriage was actually high for both sexes in the middle ages. Research points to the average age of marriage for peasants being in the early 20s for both men and women. You talk about getting a start on child rearing, but in actuality, parents were more concerned with keeping the help of their children on their own land.
This isn't totally correct. First, you need to consider how many of those monarchs died of unnatural causes. Until the Stuarts, it was expected for male monarchs to participate in war. Several kings were executed, also lowering the average age.
Next, marrying early happened to men pretty often. While you're right that wealthy men usually married in their late 20s, that was only the case for the sub-noble elite. That being, the merchants, bankers, and, lawyers who Renaissance Italians called the "popolo grosso". These men waited to marry because it took a decade or more to build up their wealth and become "real men". Because femaleness is traditionally something that is grown into, rather than earned, and because female fertility expires more quickly, women were expected to marry young.
But noble men didn't have this burden. As dukes or princes, their worth was inherent. If you look at England's nobility alone, most monarchs married in their early twenties or before. Henry VIII's elder brother Prince Arthur was only fifteen when he married Catherine of Aragon. Many other monarchs, like Henry II, Richard III, Edward I, and Henry IV married before 21.
What you said about common people marrying in their mid or late 20s is pretty correct, although this was mostly true of farmers. Marriage around age 20 was the norm for women with any means whatsoever in Northern Europe, and in Italy middle-class women would often marry as early as 12.
