For years I assumed (thanks, fiction) that marriage during these periods (edit: by which I mean from the HMA through the Renaissance, sorry) was generally between an adolescent girl and a middle-aged man. I've gradually learned through reading up on individual royal/aristocratic couples that it seems to have been more common for families building alliances and sealing peace treaties to betroth their children to each other rather than giving a daughter to a patriarch, unless there was no unmarried son on one side. But is this impression correct? And is it relevant to people other than royalty and the top tier of the nobility?
I went looking for previous questions in the FAQ and with the search function, and didn't find it. So hopefully this isn't an annoying repeat.
That's a good question.
There seem to be plenty of marriages among nobility with age differences, including brides a few years, or even many years older than the groom. The most notorious is the 20-year old John Wydville, brother of Queen Elizabeth (Edward IV) marrying the widow Duchess of Norfolk in her 60's. But it was notorious for a reason - it clearly was not common for a bride to be 40 years older than her groom!
Continuing slightly off from your question, a few other examples of older brides come to mind - Henry VIII and Katherine of Aragon had I think five or more years between them, and Eleanor of Aquitaine was nine years older than Henry of Anjou (later Henry II of England). Given the shorter life spans and state of medicine and dental care, those age differences could mean a lot.
According to this source (admittedly I don't know quite how reliable it is) the mean age of marriage in the 16th century was in the later 20s for both sexes, for much the same economic reasons that the current age of marriage is today.