My 8 year old is trying it..

My son constantly argues back about ANYTHING. And he’s getting so mouthy. He also thinks being inappropriate is funny. He keeps picking arguments with his 6 year old brother. He tells him he’s smarter and better then him. He gets my 2 year old aggravated because he tries and tease her.

I try and talk to him alllllllll the time about his attitude and he just acts like he’s not doing anything.

Any advice is welcomed.