I also have 2 boys 3 1/2 and 18 months, honestly i used to try to stop everything, now i just let them fight it out, if its yelling i make them go to their room and yell it out, now with the actual fighting (hey i wont lie its all day everyday, unless the baby is taking a nap) i do let them fight it out but if i think it has started to get to aggressive i make them stop or i get pillows and tell them to pillow fight it out, by the time i know it they are laughing and getting along. Or if they want to yell alot give them a pillow and tell them to yell in the pillow if they are going to yell other wise dont yell (you can call it the yellin pillow or something). But, dont worry Im guessing its a boy thing and boys will be boys, as much as my boys fight they also stick up for each other when they are playing with other kids and they are being mean to one of mine the other will give that kid a pop or something, so i know how ya feel, hang in there hopefully one day it will get better!! Ha we got boys lol!!