For the most part the kids get along fairly well. There is some bickering, but that is perfectly normal. They can play together and do share things without to much prompting. I try to have them sort things out on their own. When one of them comes to register a complaint about some grave injustice incurred against them by a sibling, my first question is "did you talk to them, do they know that you are hurt/offended." Inevitably they stomp away muttering, there will be a bit of shouting, and then it's over.
Sometimes the interactions are far more hilarious.
Max and Rebecca were both sitting the couch on opposite ends. She was reading a book and he was doing his homework. Periodically Rebecca would clear her throat. Max would then ask her to stop coughing in his direction. This would result in outraged protests from Rebecca that she was not coughing on him and to stop bothering her, SHE WAS TRYING TO READ.
This went on through about 3 cycles before I stepped in.
"Max she isn't coughing on you, she's just clearing her throat."
"Oh, I didn't know."
Then peace reigned over the couch.