Brian made his big league debut for the Marlins in the fourth inning of their 10-7 victory at PNC Park in Pittsburgh. He forced Bryan Reynolds to ground out before Colin Moran stepped into the box as the second batter in the bottom half of the inning. Brian began the exchange by throwing back-to-back balls, before Colin fouled off his third offering. Colin earned a 3-1 lead in the count before fouling off Brian's fifth pitch.
Brian then threw in a 71.7-mph slider to strike his brother out looking. It was the first strikeout of his Major League Baseball career.
The Marlins reliever completed the inning by hitting Josh Bell with a pitch, before forcing Melky Cabrera to fly out to right field. The Marlins took a 6-5 lead with a four-run fifth inning.
"I was a little more nervous than I thought I'd be when I saw him step in the box," Brian told reporters. "I fell behind in the count, and then once I got to 3-2, I felt like if I could drop a slider in, I felt I could get him. It was also risky, because if I missed with it, I would have looked like I didn't want any part of him. It was a high-risk, high-reward situation."
With the Moran parents in attendance, the brothers' matchup marked the first time since 1990 that a player faced his brother in an at-bat during his Major League Baseball debut, according to the Elias Sports Bureau.
"I tried to find where [my parents] were at, just to see what their looks looked like," Colin told reporters. "I was the second batter, so I was kinda peeking over. Just the support they've given us and the support I've gotten from my brother for my whole career.
"It's special just to see him follow through on his dream and achieve that. It's pretty hard to explain."
Colin went 2-for-4 with two strikeouts and a run scored in the loss. Brian did not allow a hit, a run or a walk in his only inning of work. The Marlins reliever also earned his first career win.
Brian, 30, was a seventh round pick by the Seattle Mariners in the 2009 MLB Draft. Colin made his MLB debut on May 18, 2018. The 26-year-old infielder was picked by the Marlins as the No. 6 overall pick in the 2013 MLB Draft, before being traded to the Houston Astros in 2014. Colin was traded to the Pirates in January 2018.