There is a natural tendency (or lack of it) towards being a social person. I have two kids, a boy and a girl (6.5 and 2.5). They are both smart for their age and very verbal, and of course raised in the same home, and share most of their genetic traits.
But you can already see that my son is a geek (well, what might "save" him socially is that he's tall and athletic), and my daughter is probably going to be popular. She simply has a better natural grasp of how people interact, and is much more interested in interactions, than say, imagination games. They are both very charming and outgoing, but you can already tell she has or will have better social skills.
There is probably also a snowball effect at play, too - if you have a tendency to be social, you might develop stronger social skills, etc.
I would expect the "snowball effect" to be pretty strong, especially for social interactions. Given a day where you tend to seek social interaction vs. a day when you tend to shy away from it, you can get a very different number of (practice) interactions.
There's a lot that can be learned by paying attention to other people and trying to understand what they're thinking. The earlier that someone who's not naturally adept at it realizes that this is important to pay attention to, the earlier they get better at social skills. Some of that can be highlighted for little kids while reading (story) books; paying attention to and asking questions about why the characters do the things in their interactions highlights the idea that other people do things for reasons, and that you can guess what they are (the guessing well is a skill).
not with absolute certainty, but, a. a boy who's at 95 percentile height probably won't be short, and b. he has my genes and I'm pretty tall, and so are males on his mother's side.
But you can already see that my son is a geek (well, what might "save" him socially is that he's tall and athletic), and my daughter is probably going to be popular. She simply has a better natural grasp of how people interact, and is much more interested in interactions, than say, imagination games. They are both very charming and outgoing, but you can already tell she has or will have better social skills.
There is probably also a snowball effect at play, too - if you have a tendency to be social, you might develop stronger social skills, etc.