Other parents of your kids???!
Sport has really helped me over the years but I'd like to think I'm a pretty sociable chap generally. I moved 70 miles from home 16 years ago and it didn't take me long to meet new people, whether that be through sport, work, people I met or friends of the wife. I'm still in regular contact with a handful of what I would close friends from my school days but everyone else has been since I moved away. Wife's very sociable so I've inherited a lot of her friends too, and in the main most of their other halves are cool. Some I'm closer to than others.
Then you make friends with other parents of your kid's. Some of which end up closer than others.
Consider myself quite fortunate tbh.