Photo by Mikael Kristenson on Unsplash

If you experience sibling rivalry, you may wonder how someone raised in the same household could have such a different perspective on your family dynamics.

It's not that they're lying about what happened (though that could be the case). Rather they have a contrasting memory of events, or the past affected them differently.

If you're a more sensitive type for example, slights that roll off your sibling's back would hurt your deeply. Or perhaps one of you were targeted for abuse the other neither experienced nor witnessed.

What causes sibling rivalry and why does that rivalry sometimes turn toxic? Here are 4 examples.

1. Birth order

Even when they have the same parents, children are born into different families. A first-born child, for example, may enter into a family with happy and contented parents. She receives lots of attention because no one else competes for it.

Three years later, the second child enters into a conflict-ridden household with parents who fight for various reasons. She receives less attention because it's shared with the older sibling.

Or the oldest child is born to poor, struggling parents whose stress is passed on to her. By the time the second comes around, the parents are well off financially and the second-born enjoys an environment of relative wealth and security.

And so it goes. There's evidence the eldest sibling remembers the most and is often challenged by younger siblings who say those things never happened. That's because the oldest protects the younger ones from witnessing trauma.

As a result of this protection, sibling rivalry manifests as invalidation of the eldest's experience. She realizes she has sacrificed herself to protect her siblings and now feels isolated and alone.

It's important to remember the fault for this parentification lies with the parents, not the siblings. Still, the parent's abdication leads to sibling resentment.

2. Temperament

If one child is more sensitive than the others she will internalize the effects of conflict in the family. She is more likely to be scapegoated and bear the brunt of any bullying in the household.

Taken to its extreme, temperament can include personality disorders like narcissism. A narcissistic sibling will wreak havoc on a relationship with a more sensitive, empathic sibling.

3. Attachment

If one sibling has developed an avoidant attachment style, she will denigrate a sibling who wants to connect on an emotional level.

She may use nonverbal cues such as rolled eyes, contemptuous looks, and sarcastic sighs to put a halt to any emotional connection.

Or she may appear "nice as pie" which confuses and guilts the connection-seeking sibling.

4. Resentment

If one adult sibling takes care of an elderly parent while the others live far away, resentment can build.

The caretaker sibling feels overburdened and accuses the long distance siblings of abdicating their responsibility.

Or one sibling receives more support from parents in the form of enabling or coddling. The less supported siblings feel resentful over having to make it on their own.

What to do about sibling rivalry or toxic sibling relationships

Don't ambush your sibling with a huge conversation, especially before you've asked their permission to discuss things.

Start small, with an email that says you've noticed conflict between you and want to know if she'd be willing to work on it.

If, however, your relationship feels more abusive than rivalrous, then you need to protect yourself. If they tear you down at every turn, that's the sign of a toxic sibling rather than sibling rivalry.

When a sibling gossips about you, lies about you, and turns family members against you, it's time to guard your heart rather than try to repair the relationship. Do not sacrifice yourself to keep peace with your siblings!

Don't accept non-emotional relating if that leaves you feeling empty. It's common to put up with a family member's unwillingness to share feelings to "get through" the interaction. However, you sacrifice your own needs in the process.

Focus on changing your behavior toward them, rather then hoping they will change. Set firm boundaries that teach them how to treat you and what will happen if they violate those boundaries.

If this means you must detach from your sibling, know that's not your fault. Sibling estrangement is a hallmark of chaotic family systems that don't support positive sibling interactions.

Never rely on a sibling or anyone else to validate your feelings. It's wrong for anyone to minimize your emotions. They are doing so to protect their image of what happened, and sacrificing you in the process.