Hope you don't mind a females point of view. I am currently in a class of 35. Of those 30 5 are males (just shy of 25%). The ages range from 19 to 30. I'd say that the average age of the 5 guys is early 20's.
When we first started there were a total of 60 students, and 15 of those were men (thats 25%). Again ranging from 18 to early 30's. (average age mid 20's)
You'd be surprised who you "fit in" with in nursing school. I am 38 years old (39 come april) and I have made friends with all the guys. And most of the women, they range from 18 to 30's also. I "fit in" with people I never thought I would. Different backgrounds, different beliefs, different customs, nationalities etc. I am on the opposite side of you. I am among the older students in my class. I am the 3rd oldest in my class. I am the only one of all the students that is the traditional "soccer mom" types. So like you I was worried about not "fitting in". Much to my pleasant surprise, I fit in just fine and pretty much right away. we all tend to get along and help each other.
Don't let the fear of being the youngest male in class stop you from persuing nursing. The younger guys in my class have a bit of an edge since all the "older" mom-types like me taking them under their wing and helping them along. Not to mention the attention of most of the younger women
Best of luck to you.