I have somewhat split and conflicted loyalties. My family has a deep, deep divide along Twins/Yankees lines that I could never quite reconcile in my childhood. I was a Twins fan, my mother was a crazed Yankees fan. My grandfather and most of my extended family were Twins fans, but my favorite uncle and closest cousin were Yankees fan. I was an impressionable child, very anxious to please everybody. A few of my family members resolve it by becoming bitter, hardcore fans who hate the other side. Most of us, however, choose to maintain family peace by establishing a Yankees/Twins hierarchy.
So, basically, for me what it boils down to is the following:
When the Twins play, I root for the Twins. When the Yankees play, I root for the Yankees. When the Yankees play the Twins, I root very hard for the Twins and the Yankees can go to hell. This is why I define myself more as a Twins fan. My mother is similar, except in Twins/Yankees situations, she roots for the Yankees. (But the most important thing that unites us as a family, I guess, is that we despise the Braves.)
However, I love both of those teams and pretty much could care less about any of the others (although, I do have a residual fondness for the history that the Red Sox have. But I would never call myself a fan.) If neither of them make it to the series, I default to hope that the American League will win, but I don't really care that much.
There's another home somewhere,
There's another glimpse of sky...
There's another way to lean
into the wind, unafraid.
There's another life out there...
~~Mary Chapin Carpenter