It's luck of the draw. There were 7 of us in my original group and we all really clicked, then over time we added 2 more, so now there are 9 of us. I see a couple of them at least every week and we have nights out all together as often as we can, naturally it's harder now some of them are back at work.
But there's no point in forcing a friendship just because you were thrown together. It won't work.