Kid Fights Can Be (Mostly) An Ignored Child Behavior

I just returned from shopping at the store with my 4-year-old and 6-year-old. My nerves are frayed, and I forgot to buy many of the items on my list, because my kids fought with each other the entire time. The fights are always over absolutely nothing--"he's touching me" to "her drink is bigger" (not true)--and I can't comprehend why two loving children become terrors at times. So, I researched kids fighting and have written an article on "Child Behavior: Eight Ideas To Stop The Kid Fighting." I've already tried out some for myself, especially establishing a "fight room."