The San Francisco 49ers have been a part of a brotherly rivalry once already. When Jim Harbaugh was the head coach of the Niners, he coached against his brother, John, who was the head coach of the Baltimore Ravens, twice.
In the two "Harbaugh Bowls", John and the Ravens went 2-0 against Jim. One of those games was in the 2011 regular season, and the other was in Super Bowl XLVII the following season, which we need not talk about.
In the first game of the 2025 season, 49ers fans were treated to another brotherly rivalry, this time between the Kubiak brothers, Klay and Klint.