My family has a long tradition of bad sibling relationships. The most obvious example is that of my mother’s cousins. One told the other to “drop dead” and the two did not talk again until their father’s funeral, some 30 years later. My mother’s father was supposedly in love with his brother’s wife and so ran away at 16 to join the Marines. My grandmother on my father’s side bitterly resented her brother going to law school and thus having opportunities for his family that she, although a college graduate, did not. My father’s father and his siblings were separated by an ocean while they were still very young.

My grandparents were all immigrants and given the scarcity of material or emotional resources available in their families, it is not a surprise to me that siblings of their generation did not get along. My own sister and I fought bitterly for most of our childhoods because of this lack of resources, although in our case what was mainly lacking was time, attention, and affection. Our parents fought a lot during our childhood, so we grew up believing that yelling at the top of your lungs at each other is a perfectly normal way to communicate at home, or in a mall, or in the car, or really, anywhere.

One of the things I’ve been proudest of with my own family is how well my kids get along. I have always attributed a lot of my children’s lack of fighting to the fact that there isn’t much to fight over. We have enough materially to get by, and both my husband and I shower attention and affection on both children. My husband and I do not fight often, and when we do, it isn’t very loud. My children do not see yelling as a normal way of talking as I did at their age. In fact, they become frightened if I simply talk in what they call a “mean tone of voice.”

I also attribute the peace to luck. My children are barely two years apart, so they watch the same shows, listen to the same music, and have similar interests. Having the oldest be a girl with a highly developed maternal side and the youngest a boy who eagerly accepts adoration doesn’t hurt either. But last week, I realized that really, there’s only one explanation for our calm, family life – my daughter has the patience and strength of Superman.

Last week we went on vacation and brought my daughter’s best friend with us. All three children have always played together beautifully and we’ve had the other child for extended overnight visits before. But perhaps because the three have been separated from each other for a few months, their dynamic was different this time. Almost from the first day the friend and my son fought. They fought like siblings. Phrases I’ve never heard before like, “He’s looking at me” and “Well, she hit me first” were screamed at the top of their little lungs. Both children are very bright and they could not stop picking each other’s most vulnerable points to poke and jab.

I believe the resource they were fighting over was my daughter. Each wanted her undivided attention. Of course, a girl who gets scared at a “mean tone of voice” does not react well when two of the people she loves best in the world start yelling. So, every time my son and our friend would start to yell, she would retreat either physically to another location, or if we were in the car, in to herself. This left the other two angry at each other for driving her off, and with nothing else to do, they would start to fight all over again. My “mean tone of voice” got louder and louder with each passing day.

Having now spent a week watching the way most siblings go after each other, it seems stranger to me not that my mother’s cousins leapt at the chance not to talk for 30 years, but that anyone ever learns to get along with his or her sibling. If you spend the first 18 years of your life locked in a battle where even looks are malevolent, how can you ever establish a decent relationship? Every comment, every look is an opening for a further wound. It’s like living in your own private war zone. It explains why well into adulthood, my uncle, the father of three children himself, took my father bringing a nice shirt on a family camping trip as a reproach of his own hygiene. Why my father could work himself into a rage over the fact that his mother had agreed to keep his younger brother’s dog in the house. Even though my father rarely visited the home several states away. It explains why my friend cannot ask her brother how the keyless lock on his car works without him blowing up at her and accusing her of playing helpless. If you grew up fighting with your sibling, you are forever combatants.

Which is why I’m so grateful for my daughter, a conscientious objector. My son is obnoxious. He is loud and grumpy and difficult and would gladly cut off his perfect little nose to spite his face. In fact, given how good looking he is and how often strangers tell him that, I’m afraid one day he actually will physically maim himself to keep the rest of us from enjoying looking at him. But, he is also the sweetest, most cuddly boy on Earth.

My children’s fights are like the big fight in Superman 2. General Zod realizes that Superman’s great weakness is not kryptonite but that he cares about humans. So, Zod threatens humans and Superman can’t do much about it. This is how my kids are. My son is General Zod but my daughter is Superman. The fight can’t go very far because my daughter doesn’t want anyone, including General Zod, to get hurt.

With no one to bounce his grumpiness off of, my son quickly reverts to his sweet self and peace reigns in our happy home. Until last week when General Zod finally had an enemy equal to himself, I never knew how much our family depended on our Superman.