What to do with fighting boys

I have to sons ages 10 and 11 who like to have a lot of fun together or fight together. There is no middle ground. Is this normal for boys? (We had 5 girls first and I had no brothers so I'm winging it here. ) Anyway, today they were to have their room clean to go the Football Hall of Fame. Each one insisted that he was doing all the work and the other was not doing anything at all. Sound familiar? I got tired of refereeing constantly and needed something else to try or go crazy trying to figure out how to make them get along and get the work done. I got out the book Creative Correction by Lisa Welchel and looked under WW3, sibling squabbles. I called both boys down and made them stand on opposite sides of the yard yelling to the other "I love you, brother." 20 times. By the end of it they were laughing and now they are upstairs working together; at least for now.