Every size family has conflicts, but the larger families have more. They are completely unavoidable, although I believe that every conflict is potentially avoidable, or at least manageable to a peaceful conclusion.
What do we struggle with most? Other people and our own desires.
"What causes fights and quarrels among you? Don't they come
from your desires that battle within you?" - James 4:1
So how do we deal with other people? Let them walk all over us so they get THEIR way while we behave as doormats? I don't believe so. Here's what I do to train my children.
Whenever there is a conflict, (raised voices, crying, whining, etc) I gather all offending parties. One at a time they tell me what happened. If another child interrupts with "No, that's not what...." I immediately shush them until the first child has told me everything. Then the second child tells his story. I then go back and forth between them, asking if that actually took place until I get to a story that they both agree on. Most of the time this takes seconds, but sometimes it can take several minutes.
I then ask each child what they did wrong and what they should have done.
One of the answers is (and should be) "I should have asked nicely first." That's my basic family rule that I repeat all the time. ASK NICELY FIRST.
Does someone have your toy? Don't snatch it - ask nicely.
Did someone snatch a toy from you? Don't scream like a ringwraith - ask nicely.
Once they see what they did wrong, then I have them apologize to the other child and give them a hug. Often they are both wrong and both must apologize. And if they give some lousy half-hearted hug, I tell them to do a bigger hug. Pretty soon somebody's feet are off the floor and they are smiling. It's so important to do that!! The fun hug restores the relationship like nothing else, and they are ready to play together again until the next conflict 10 minutes later.
What if a child broke something that someone else made? Well, asking nicely doesn't fix the problem, but it can help heal the relationship (which is what it's all about anyway). Inform the person that they were hurt by them breaking their creation, and please (here is the asking nicely) do not do that kind of thing again.
Apology, hug, restoration, but the hurt is still there for the victim. Maybe it was something special or expensive. But what's more important? The item or a good relationship with your sibling?
When they get out into the world, they will have these same issues, only with adults (but many adults they deal with are going to act like children). The same principle applies. Ask nicely first. Is your neighbor parking on your side of the street so you have to park elsewhere? Ask nicely first. Neighbor kids doing things in your yard? Ask nicely first. Co-worker causing you trouble? Ask nicely first.
Husband leaving the toilet seat up? Ask nicely first.
Wife leaving 436 articles all over the entire bathroom? Ask nicely first.
Those three little words are almost a magic cure-all for most relationship issues.