My boys are similar in their activities. They are constantly connected at the hip and the best of friends... with many sibling fights. It's like they have their own language and rules, and no one else really gets it.
I had to teach them and repeatedly tell them about soft touches, being gentle, sharing, not taking things out of the hands of the other. I still keep encouraging them to use their words, gestures and come get an adult if they need help... instead of fighting or asserting their power. I don't let them scream. I tell them to use indoor voices, to whisper, or to be quiet. I talk quiet when I say whisper and quiet, so they understand what I'm saying. I teach them short phrases, words and gestures they can use to get their point across.
When they couldn't really say much, I showed them a few sign language gestures such as please, thank you, more, etc. There are children't sign language books you can get for infants. I encourage them to communicate by using the sign and speaking the word at the same time. Then I show them what it means.
They need to learn to respect each other's space and boundaries. These habits may begin to be practiced with other children as they grow older, so it's important to address them now with communication, encouraging sharing and learning boundaries.