They are in control of their actions and they make their own choices on how to behave. Set the example for your children. As always, your kids are watching how you deal with others. When dealing with other people you almost always have to compromise. Learning people skills is indeed a skill.
Some people are very adept at it while others struggle throughout their life with it.
Learning to compromise and negotiate and to be tactful is something that can begun to be learned in childhood and it s up to parents to teach the kids. Finally, hang in there and be patient. Know that every family has children that bicker and argue at one time or another. Remember too that our children use their family as a practice ground. They will practice certain behavior, actions, and verbiage on their own family before they will with the outside world.