I was 26. I started uni at 22 and did a foundation year, and there was a whole mix of ages in it (lots of people in their 20s, but also a few people in their 30s and 40s).
I then did a masters, and then ended up with 2 years out before doing a PhD. I was already starting to feel 'behind' with my undergrad, but then I felt 'behind' people I was at uni with, some of whom were already getting towards the end of their PhD as I was starting mine. I was thinking about it recently though when I realised a guy who was in my year at undergrad is now a year below me in my PhD-it might seem like everyone's doing things at a set time, but really it's not as much the case as it seems. People do all sorts of expected milestones at all sorts of different ages and times in their life (or not at all, not everyone has a dream job for example, some people are happy just working to allow them to do the other stuff they really want to do). Life's not a race.