I ask the twin 2 year old boys that everyday at work. Usually their answer is to break out in a wrestling match where one will tackle the other to the floor and then sit on each other’s backs so they they can’t get up. Usually I have to jump in and rescue the one that’s laying on the floor. So I think the answer is: Siblings would rather fight. Honestly growing up I always got a rise out of fighting with my older sister while being very protective of the other one.