College (1): Duke Blue Devils
I became a fan when I was 8. My parents and my brothers root for the rival North Carolina Tar Heels, but that didn't stick with me. One of my friends in third grade was a Duke fan -- I assume maybe his dad was -- and I think that's where I got my rooting interest from. Age 7 or 8 was a defining period for my rooting interests in sports, which we'll see again later.
College (2): Florida State Seminoles
Why two teams? Good question! (And this isn't the first time you'll see two.) Duke has historically not been good in football, but that's not the compelling reason. The truth is, when I was around 13 or 14, a lot of kids in the area started rooting for the Miami Hurricanes. This kind of drove me crazy (also a pattern), so my recourse was to find their rival and start rooting for them. Immature? Maybe. But i was 13. In my area, it was not uncommon for people to have multiple college teams they supported, the only "rule" was no supporting each of a pair of rivals. Anyone who did immediately had their sports fan card revoked.
NFL: San Francisco 49ers.
Age 7. Super Bowl XIX, the 49ers were playing the Dolphins. My neighbors came over to watch the game with us. We had takeout from a burger place, and they gave away miniature helmets for each of the Super Bowl participants. My favorite color as a kid was red, so I liked the 49er helmet better, and a rooting interest was born. When I was younger than that, I literally thought all football players were called "cowboys" (which was confusing, given the other cowboys I was familiar with) because they were my father's favorite team.
MLB (1): Los Angeles Dodgers
I don't even have a story on how I developed this rooting interest. I just know I was around 10 or 11 and started following them in the standings, and I think I liked the Dodger blue. My cousins were Braves fans, but that didn't stick with me.
MLB (2): New York Yankees
OK, on this one, I can be properly accused of maybe jumping on a bandwagon. I have no idea, and that wasn't my intention, but I did start supporting them in 1996 during the World Series, and I can't even use youth as an excuse (I was 19). But I can explain. In 1991, the Braves got good all of the sudden, and all the kids at school started wearing Braves hats. Remember the Hurricanes above? That drove me crazy! In 1996, they were back in the World Series, had just won it in 1995, and I was rooting hard for them to lose. Somehow, that negative energy for one side converted into positive energy for the other --- possibly because the Yankees once used the local minor league team (Greensboro Hornets, then Bats, now Grasshoppers) as an affiliate and a few Yankees (including the young Derek Jeter) had once played in town. And surprisingly, this is the one rooting interest I share with my dad. I didn't learn until that same series that he was a Yankees fan (we didn't watch much baseball in the house before that).
NBA (1): Charlotte Hornets
This is the one local pro team I'll care to support (I don't watch enough hockey to talk about the Carolina Hurricanes). I live in Charlotte now, and I've lived in North Carolina my whole life. When the Hornets first came to town, it was a big deal, as that was the area's first professional team. I'm not a huge supporter -- I don't go to games, don't try to watch every game -- but I appreciate their existence, watch games from time to time, and the return of the Hornets name is welcomed (the Bobcats moniker just didn't have any appeal).
NBA (2): Cleveland Cavaliers
Come at me! I like this team because of Kyrie Irving. Dude spent one year at Duke -- and only played 11 games -- but I loved watching him play, and I loved his attitude on the bench when he was injured. He was at every game, first guy off the bench to congratulate a teammate, celebrating every success, and then returned for the NCAA tournament and played like he never missed a beat, despite being out since late December. (Of course, his return disrupted the team's basketball cohesiveness and chemistry, since they had learned to play without him and didn't have the opportunity to get a few games under their belts with him back in the lineup before the tournament.) With LeBron back, I admit it makes the team better and more watchable, but I support the Cavaliers' efforts because of Kyrie.