I am an only child, married to my sweetheart that I dated for five years and married happily ever after :) One grave issue haunts me when I check updates on Facebook. From kindergarten to 10th grade I studied in one convent school. All my solid formative years have been at one place but I do not have any friends from that time, kindergarten through high school.
I have a bunch of awesome friends from my college days, from the work place, and also from my masters program. But I feel the dearth of not having friends from grade school. I think that's probably because people around me talk a lot of about school days, quote their unforgettable naughty an adventures from school. They talk about that one friend from school that they can bank on for the rest of their lives. Even my husband has a lot of friends from his pre-school days.
In school, I always had to go out of my way literally begging and bargaining people to be my friends and I felt shunned. I remember one incident in 7th grade when I went crying to my math teacher and told her not a single soul was a friend. She took pity on me, held me, and announced in class that she would be my best friend from then on. I was innocent and foolish and really believed she would be my friend from then on.
Personality insight: I am pretty with dimples :), smart with an affirmative voice and good communication skills. I love talking and making friends on the fly. I am from a well-educated family. My father is a professor of English, mom lecturer of Economics. I have been the doting daughter and granddaughter. I have been the apple of the eye for my grand parents. I love pets...especially I'm a crazy feline lover.
Sure it's nice to have childhood friends with whom you can share memories. But like you, for a variety of reasons, many people have had difficulty making friends when they were younger.
They may have been different in some way and school kids are quick to pick on someone who is prettier, homelier, smarter or dumber. Also, kids often seize upon the way a classmate speaks or dresses, or are critical about some other aspect of a schoolmate's personality.
Whatever it was, there is no reason to go back and analyze what happened then. It may have been a combination of factors. Now you have had success at making friends—at college, graduate school, and at work—and if you are lucky, one or two of these relationships may turn out to be close and long-lasting ones for you. It's nice that these people feel close enough to you that they want to share their childhood memories.
My advice: Focus on these friendships rather than the ones that got away. Many people use Facebook to reconnect with people from the past but if that wasn't the best time of your life socially, don't spend another minute lurking on the Facebook pages of people you probably wouldn't want to be friends with now. Remember too, after they have shared their "pirate adventures," they may not have anything else to say to each other.
Hope this helps.