Where does the Red Sox fandom come from?
NBC Sports Boston reported on April 1, 2021 that Klay Thompson posted an old photo to his Instagram page showing him in a Boston Red Sox uniform as a kid. According to the outlet, he explained in the caption why the Red Sox were his favorite team growing up. That makes the report about his own Instagram post, relayed by the outlet, rather than a quote from an interview.
The geography does not point to Boston. Thompson was born in Los Angeles on February 8, 1990, and when he was two his family moved to Lake Oswego, Oregon. He went to Santa Margarita Catholic in Rancho Santa Margarita, California, played at Washington State, and was drafted 11th by the Golden State Warriors in 2011. The Red Sox won the World Series in 2004, when he was 14.
What about the Tennessee Titans?
The Titans tie is thinner. A Ticketmaster Blog item says "NBA players Klay Thompson and Gary Harris have also staked their claim publicly as Titans fans." The item carries no date and no quote from Thompson himself, so it is a background tie and not a stated fandom.
Questions people ask
What team did Klay Thompson root for growing up?
NBC Sports Boston reported in April 2021 that an Instagram post of his explained why the Boston Red Sox were his favorite team growing up.
What is Klay Thompson's favorite MLB team?
The Boston Red Sox, according to NBC Sports Boston's report on his Instagram post.
What teams does Klay Thompson root for?
The Red Sox are reported by NBC Sports Boston, and a Ticketmaster Blog item links him to the Tennessee Titans as a background tie.