The sIMiLaR clAss aND EdUcATioN anD taX bRackET thing is mostly a matter of networking. There's a ton of hobbies and interests that can appeal to a wide age range. Movies, music, literature, ritualistic cannibalism, video games, sport fandom, rock climbing, painting, sculpting, anarcho-communism, board games, skydiving, photography, crocheting...
...dogs, making those intricate book nooks with mirrors that make them look bigger on the inside, true crime podcasts, tabletop wargaming, cooking, eating, cat shows, cheese rolling, roadkill taxidermy, crossfit, ren faires, horse riding, vivarium design, vegan activism, omegaverse slash fiction... to name a few.