Fight, Lie, Play Innocent...

Okay so my son (he's eight) and my daughter (she's 5) have been having issues with each other lately. She's bothering me...He's not sharing...You know normal sibling rivalry. Well my darling son gets rough with my daughter and when she tells, he says she's lying. He didn't do anything. Well I'm not deaf or blind and certainly not stupid, hell I have a little brother myself, so when those eyes come out (and moms you know the eyes I'm talking about) I can tell he's lying. So it takes but three minutes for me to get him to tell the truth. You would think by now he would know I can hear them fight. I can see the facial expression and know who is telling the truth and I remember the crap I tried to pull with my mom when I fought with my little brother. And I catch him or her if its her every time....but no we still fight, lie, and play innocent.