It's the first time in NBA history that brothers have faced off in the conference finals.
Stephen spoke to ESPN's Rachel Nichols about the playoff matchup.
The two-time NBA MVP says it's weird playing against his brother. He can't turn off the desire to cheer for his brother even though it may hurt his team if Seth plays well.
"When I was guarding him yesterday, he had a corner three in front of our bench, and it's such a mixed feeling," said Stephen. "I can't really turn it off to be honest, I'm like, 'Oh, I'll be OK if he makes this one, I'm still going contest really hard because it looks good on film, but I might be OK with him making it.'"
The Curry brothers will face-off in game 2 on Thursday night in Oakland before they compete again.
"It's a weird vibe. It's the best way to explain it," said Stephen. "I can't turn off that human nature in that moment to root for him."
Game 3 will be on Seth's home turf in Portland.
See Stephen Curry's interview on Good Morning America.
You can catch my conversation with Steph Curry on Good Morning America - including what it’s like having your mother wearing the gear of the other team when you’re trying to get to the NBA Finals 😂 pic.twitter.com/56RuAPWb3I— Rachel Nichols (@Rachel__Nichols) May 16, 2019