I've been to 8 home games this year and have seen more than 8 fights in the bleachers. There was a brawl today that went on for almost 10 minutes before security started taking away at least 1 guy (Cubs fan of course) in cuffs.
It's not just Cubs/Sox it's been going on all year. Seems to be across sports this year and IMHO it's probably people going way too hard on the liquor after 1+ year of not being able to attend games in addition to heightened anxiety during COVID.
If you are taking kids to the game I'd avoid the bleachers. If you really want to sit in outfield the right and right-center seats seem to be much tamer.