Are there any long term consequences to two brothers fighting all of the time, they are 12 and 13yo?
No. Not unless you count all your property damage that they inflict while fighting! This is normal sibling rivalry and will get better with age and maturity. At least hopefully! :).
No. Not if this is normal sibling interaction and they get along fairly well in between their arguments.
Usually not. In kids, there usually is a certain amount of sibling rivalry and competitiveness. I allow no slack for physical altercations, holding both kids responsible for avoiding dangerous fighting. Everyone suffers thge "punishment" for fighting. For verbal scuffling, I chase them to another room to settle it. And lots of discussion explaining potential harm helps.