Toxic Siblings and Sibling Rivalry: Long-Term Effects

Explore the long-term effects of growing up with a toxic sibling and the deep-seated impact of sibling rivalry. Learn how early childhood conflicts shape relationship patterns and mental health, and discover strategies for healing and fostering healthier relationships.

Let’s dive into the real talk about growing up with toxic siblings. Forget the minor sibling bickering over video games or clothes. We’re talking about a deep-rooted, damaging rivalry that doesn’t merely disrupt your childhood – it winds up messing up your perspective on relationships for life.

Here’s a typical scenario of a darker sibling rivalry situation.

You’ve just completed what you feel is an award-worthy science project—a volcano that actually erupts. You should feel proud, right? But along comes your sibling, who not only downplays your achievement – but tells your parents a wildly exaggerated story about how you nearly burned the house down in the process. It’s not just a comment. It’s a full-blown character assassination — and a total fabrication.

But it doesn’t stop at a single science project. Your sibling becomes a consistent heckler – demeaning you – lying about you – hurting you in an abundance of ways.

This isn’t just “kids being kids.”

It’s a formative experience teaching you that the closest people in your life can also be the ones who hurt you the most.

Worst of all – this isn’t like dealing with a schoolyard bully where you might find refuge at home. This tormentor shares your home, your parents, your space. You’re trapped in a car with them for every family road trip, seated across from them at every meal.

Unfortunately this constant psychological warfare can wind up teaching you –  the victim sibling – to always be on guard, to constantly wear emotional armor (even in your own home), and to expect betrayal and attack at every turn.

The Seeds of Sibling Rivalry

Why Some Siblings Become Toxic

Growing up with toxic siblings can stem from various underlying reasons beyond mere personality clashes. Here are some of the core factors that contribute to such dynamics:

1. Jealousy: When siblings vie for parental attention or resources, jealousy can breed resentment. This can escalate if one sibling perceives another as being favored or receiving more support, whether in terms of affection, opportunities, or material goods.
2. Personality Disorders: Mental health issues, including personality disorders, can complicate sibling relationships. These conditions can lead to unpredictable or manipulative behavior, making the familial environment toxic.
3. Disruption of Birth Order: Birth order can play a significant role in shaping sibling dynamics. For example, an older child may feel dethroned when a younger sibling is born, leading to resentment. Similarly, the youngest might feel overlooked or less capable, fostering insecurity and competitive behavior.
4. Unresolved Family Issues: Sometimes, the roots of toxicity go deeper into the family’s history. Issues like parental favoritism, inconsistency in discipline, or even parental neglect can lead siblings to act out against one another. In families where open communication and emotional support are lacking, siblings might not learn healthy ways to resolve conflicts or support each other, instead developing antagonistic relationships.

One of the more insidious long-term effects of growing up with a toxic sibling?

The normalization of unhealthy relational patterns.

If your primary model for a close relationship involves manipulation, rivalry, or emotional distress, then here’s a significant risk that this will become your “normal.”

In fact, research studies suggest that sibling relationships are among the most influential in our lives, particularly in how we form our identities and relational patterns.

According to a study published in the Journal of Family Psychology, intense sibling rivalry and conflict can lead to increased anxiety and depression in adulthood.

So, it’s not just a rough childhood you’re getting. It’s a setup for long-term emotional issues.

Dr. Jane McGregor, a sociologist at Nottingham University, notes that being a victim of toxic sibling rivalry can lead the victim sibling to unconsciously seek out similar dynamics in their adult relationships, as these feel familiar, even if they are unhealthy.

For example…

• If someone used to being manipulated by a sibling, then they might not recognize controlling behaviors in a partner as red flags.
• Instead, they may interpret them as normal or even signs of affection.
• This dynamic can play into the selection of toxic partners, perpetuating cycles of unhappiness and dysfunction.

Another example…

• Let’s say the victim sibling meets someone who treats them with respect, who offers kindness without a hidden agenda.
• Well… If you’re used to sibling interactions defined by toxicity, your first instinct might be disbelief. Or you might be constantly waiting for the other shoe to drop.
• Meanwhile… if someone does come along mirroring the manipulative traits of your sibling? Well, that feels like home.

Next up… let’s dive deep into how how to break the cycle and reclaim your story.

Breaking the Cycle Of Toxic Sibling Rivalry

Alright, let’s get down to brass tacks. Breaking free from the long shadow of a toxic sibling isn’t just about moving out and moving on. It’s about a deep, sometimes painful introspection and an outright rebellion against the crappy hand you were dealt.

Here’s how to start:

Tip 1: Embrace Self-Reflection

This isn’t about navel-gazing or self-pity. It’s about taking clear mental inventory of your past so you can improve your present.

Imagine you’re sorting through your attic, tossing out what doesn’t serve you.

Write down every crappy thing your sibling did that ticks you off. Then notice if there’s a pattern in the people you choose to hang with.

• Does your best friend manipulate you like your brother did?
• Does your girlfriend make snide remarks like your sister?

Pinning this down can be a revelation and the first step toward not walking into another emotional ambush.

Example: Let’s say every time you brought home a win—be it a school award or a new job—your sibling undercut you. Now, if your current partner throws shade on your achievements under the guise of “keeping you grounded,” guess what? That’s not grounding. That’s a replay of your past.

Tip 2: Cultivate Healthy Relationships

Look, you’ve got to know in your heart what a healthy relationship looks like. It’s time to remind yourself that these types of fulfilling relationships exist. So, get out there.

• Join clubs, volunteer, be part of communities that foster support and encouragement.
• Watch how people in these groups interact.
• Notice the give-and-take, the respect, the way conflicts are handled without someone sleeping with your ex just to get back at you.

Example: Join a hiking group or a book club—anything where people come together to share positive experiences. When someone offers a compliment or constructive criticism, observe how it’s done with respect and without a hidden dagger. These are your role models.

Tip 3: Practice Assertiveness

It’s time to learn how to say what you think and feel without being a jerk or a doormat. Assertiveness isn’t about being loud or bossy. It’s about being clear and respectful.

Take a class, read a book, or even watch tutorials.

The goal?

To express your needs and boundaries firmly and respectfully… so that you’re no longer an easy target for the toxic people who seem so damn familiar.

Example: Next time someone tries to push your boundaries—like that friend who always expects you to pick up the tab or that cousin who thinks your apartment is their vacation home—state your limits clearly. “I can’t cover your meal today,” or “I need my space this weekend.” It doesn’t have to be a fight. It’s just stating what’s true for you.

You need to set those boundaries like you mean it.

This might mean dialing back on family time if your toxic sibling is going to be around. This isn’t about creating drama. It’s about protecting your mental health. Choose who gets the privilege of your time and energy.

Recognizing the warped lenses handed down to you isn’t about blame. It’s about finally seeing the world in widescreen, where not every relationship is a battlefield.

Learning that vulnerability isn’t a weakness but a strength can be a game-changer. It’s understanding that good people exist and letting them in can enrich your life.

Conclusion: Toxic Sibling Rivalry

The scars of growing up with a toxic sibling can run deep, shaping how one navigates the world in fundamental ways. But these scars don’t have to dictate one’s destiny. By confronting these painful truths, by relearning what healthy relationships look like, and by choosing every day to strive for better, it’s possible to not just survive, but thrive.

It’s a journey of transformation—one that starts with a simple, powerful act of belief in something better.

And from there, the healing begins.

If you want further support to boost your self esteem, work with me in 1 on 1 coaching sessions to strengthen your mindset. And check out my therapist recommended program The Anxiety Cure.