Couple of ideas.
First set some ground rules on what is ok and what is not ok to say to each other, like no name calling, no hitting ect and tell them what the consequences of those will be, like a quarter in the ajr for every name you call or washing the toilet, if you have a dirty mouth you can do a dirty job. YOu can never have too clean a toilet. :)
Then when the nexy time arises, be very calm, don't raise your voice, smile and tell them the consequences. Then follow threw.
If it is something else and they just can't get along, let them fold laundry while holding each others hand so they only have one hand each to fold with, team work!
Or have one sweep and the other move chairs, and hold the dust pan.
Anything that requires team work.
Sometimes when my boys fight I tell them to hug and make up, they say eww and I say, I can make you kiss too. I always get that hug, haha!
Remember there is never an excuse for bad behavior, not ADHD, Not tired, not hungry, not sick, nothing so hold them accountable! And then be consistant, let them know you are done letting them hurt each other and that there is a new sheriff in town ;)