6 Reasons Adult Siblings Fight

Mothers have a role to play here, too. One study from Cornell University revealed that 70 percent of mothers in their 60s and 70s felt closer to one child over another.

Whether real or perceived, the effects of favoritism have been shown to last from childhood to later years, even lasting after the death of a parent.

3. Aging parents

The birth order dynamic routinely plays out once parents need increasing assistance.

“In most families, everyone has a role,” says licensed mental health counselor Jody Mykins, from Irondequoit, New York. “Often, the older child is given more responsibility. This can continue in later life with aging parents; the older child is expected to carry more of the load for caretaking [while] the younger sibling may feel left out of decisions.”

Gender may also come into play. The Caregiving in the U.S. 2020 report, the latest available, showed that the majority of caregivers — 61 percent — who make medical appointments and otherwise provide care to a parent are women. So it’s possible sisters may shoulder a larger burden.

4. Jealousy

If siblings feel there is a limited amount of something — such as love, support, affection or basic resources — they may feel as if they need to compete, especially if their parents weren’t generous with love, affection, praise or support, Conner says.

“Depending on the perception of the child, it can easily appear as if the sibling is receiving something that they were not the benefactor of,” Conner says. “It feels unfair, and fosters a spirit of jealousy.”

5. How families define success

 Mykins says an outgoing child, or one who reaches high levels of achievement in academics or athletics, “may receive more parental attention than a sibling who is quiet and introverted.”

That can cause sibling rivalry. Siblings can become resentful when parents focus heavily on the child that, say, earned a college diploma, while ignoring or downplaying the success of another child who didn’t seek higher education.

If that is not how a family defines success, then the parents may not think, “He has a good job, he supports his family, he’s happy,” Mykins says.

6. Grandchildren

A sibling with children may spend more time with their parents than a sibling without children, leaving the latter feeling ignored, Mykins says.

If this is the case, she continues, have a conversation. It's perfectly reasonable to bring up that the family doesn't consider that the childless sibling might want to host for the holidays, for instance.

Or the aggrieved sibling could say, “We always plan things around their schedule. I don’t feel as important.”

Strategies for coping with sibling rivalry

Be proactive. Mykins, 56, suggests having open discussions with siblings about unhealthy relationship patterns before a crisis arises.

“Don’t wait until your dad is in the hospital, or your mom needs nursing care, and you need to figure out quickly what to do,” Mykins says. Waiting only increases stress, which can increase tensions.

And if you're dealing with an estate or will, get a neutral third party ahead of time. They can minimize the strain by making sure the intended desires of the will are realized. Siblings entitled to the same assets but unable to agree may decide to liquidate them and split the proceeds.

The conversations may not be easy, but there are ways to mitigate damage.

“Be honest, open, willing to listen to the other person and willing to consider making a change,” Mykins says.

Look inward. The only thing that we can control in this world is ourselves, Conner says.

“The root cause of conflict is the perception of each of the participants in the conflict,” she says. “It is their thoughts about what is, what should be or what shouldn't be.”

Conner advises doing some self-reflection.

“The first step is always going to be an acknowledgment that you have some ownership to the rivalry—no matter how big or small,” she says. “Making a decision to address your part, and to do your work is critical.”

 Specific questions to help with self-reflection include: Why do I feel this way about my sibling? How have I contributed to this conflict between me and my sibling? What type of sibling do I want to be for them, regardless of what they do?

Answer honestly and decide whether there are alternatives for why you may feel the way you do, Conner says.

Set boundaries. Setting healthy boundaries with a sibling isn’t about handing down an ultimatum. Think of it as an act of love to buoy your bond.

“Boundaries let your sibling know exactly what is and is not OK with you in terms of your relationship,” Conner says. “Oftentimes, people get upset when their ‘imaginary boundaries’ are disregarded and violated, when the reality is they have never been clearly communicated—or they have been communicated, but the consequence for the boundary is never actually followed through with.”

This isn’t easy. Especially if a boundary is outside of what is expected within the family dynamic, holding tight to it “can be scary and possibly alienating,” Conner says.

Be open. A sibling rivalry is two-sided, Conner says, so you can make the decision to participate in that rivalry, or step away.

“Developing a deep self-awareness will allow you to show up in the relationship in a way that makes you feel proud of who you are being,” she adds. “When you aren't clear on who you are being and how you are showing up, you don't grow or make adjustments in order to be the best version of yourself.”

Because family issues frequently get messy, it can be good to have a therapist listen to conversations and weigh in.

Says Mykins: “It may be an opportunity to heal some very old wounds.”

Editor's note: This article was originally published on January 6, 2023. It has been updated to reflect new information.