When Adult Siblings Don’t Get Along, Is It Really “Because of Mom”?

Why the Mother Often Ends Up at the Center of the Story

3) Triangulation: when siblings become a pressure valve

In many families, siblings do not just “have conflict.” They are recruited into it.

Family systems theory describes triangles as a basic way families manage anxiety: when tension rises between two people, a third person gets pulled in to stabilize things, consciously or unconsciously. 

Examples look like this:

• A mother vents to one adult child about the other.
• One sibling becomes the “responsible one” who is praised for compliance, while another becomes the “difficult one” who gets blamed for conflict.
• The family avoids direct disagreement by outsourcing it into sibling rivalry.

Over time, siblings can start relating to each other through the triangle: as allies, as competitors, as witnesses, as scapegoats. The mother may not even intend harm, but if she is the emotional hub, triangulation can form around her simply because that’s where the emotional weather is being tracked.

Caregiving: The Stage Where Old Roles Become Loud Again

Even siblings who were “fine” in their 20s and 30s can fracture when parents begin to need help. Caregiving decisions activate:

• Old fairness arguments (“You always got away with everything.”)
• Old identity roles (“I’m the fixer.” “I’m the outsider.”)
• Old injuries (“Mom never saw what I carried.”)

This is not hypothetical. Research on sibling dynamics in parent care notes how unresolved rivalry and questions of “equal obligation” can resurface when parents need support. 

And the context matters: family caregiving is widespread and rising in the U.S., with tens of millions of caregivers, and women still representing a majority. 
When caregiving lands unevenly, sibling relationships often become the battleground for deeper questions: Who is loyal? Who is selfish? Who is “good”?

In many families, the mother is the person receiving care or directing it, so her preferences can amplify sibling tensions, intentionally or not. If she leans on one child more, praises one child more, or complains to one child more, it can re-ignite the family’s original “role assignments.”

The Part We Avoid Saying Out Loud: “Mom” Can Also Be a Symbol

Sometimes the mother is not the problem as a person. She is the symbolic site where siblings are still trying to resolve:

• Who was lovable.
• Who was chosen.
• Who had to earn belonging.
• Who got protected.
• Who got blamed.

That is why adult sibling conflict can feel strangely young, even when everyone is in their 40s, 50s, or 60s. The argument is about today’s logistics, but the emotion is about yesterday’s meaning.

This is also why a mother’s smallest behaviors can feel enormous. A casual comment like “Your brother always checks on me” can land as a lifetime verdict.

But Is It “More Often Than Not” the Mother?

Here is the honest answer: the mother is often involved, but not always culpable, and rarely the only factor.

Adult sibling friction can come from:

• Personality differences and incompatible values.
• Unequal money outcomes, inheritance fears, or financial entanglements.
• Spouses and partners reshaping loyalties.
• Trauma histories that siblings experienced differently.
• Distance, resentment about effort, or uneven emotional labor.

Also, focusing only on “the mother” can accidentally erase:

• The father’s role (including absence, favoritism, or conflict avoidance).
• Cultural expectations that burden mothers with kin work.
• The reality that many mothers were parenting inside their own stress, depression, economic pressure, or untreated trauma.

So the most useful framing is not “Mom caused this.” It is:

The sibling relationship is living inside a family system, and the mother is often the system’s most powerful relay point.

That framing keeps empathy intact while staying specific about patterns that can be changed.

No two children grow up with the exact same mother, even in the same house, because she shows up differently to different needs, temperaments, and seasons of her own life. What feels like love and protection to one sibling can feel like pressure, comparison, or invisibility to another, and both experiences can be true at the same time.

When Mom Is Actively Fueling the Fire

But sometimes the tension is not just an old echo of childhood roles. Sometimes a mother is still actively stoking sibling conflict through comparisons, private venting, selective storytelling, or turning one child into the “translator” of the other. In those cases, the task for adult children is not to diagnose her motives or win an argument about the past. The task is to stop being usable in the conflict.

The most effective move is to step out of the triangle. That can sound like: “I’m not going to discuss my sister/brother when they’re not here,” or “If you want this resolved, it needs to be a conversation with all of us.” It can also mean refusing to carry messages, refusing to compete for the “good child” position, and moving sensitive family decisions into shared group communication so facts stay consistent.

This approach can feel harsh at first, especially for the child who has been rewarded for loyalty and emotional labor. But it is often the only way to protect the sibling relationship from becoming a proxy war.

If You Want Peace, Stop Asking “Whose Fault” and Start Asking “What Pattern”

Blaming the mother can feel satisfying because it creates a single cause and a single target. But families are not single-cause systems. They are pattern systems.

If adult siblings are in friction, parents are often part of the origin story. Mothers are often more visible in that story because they are frequently the emotional hub, the kinkeeper, the one whose approval and attention carried outsized meaning, and the one whose needs now organize the family’s logistics. 

Still, the most hopeful truth is this: patterns can be interrupted. A sibling relationship does not have to remain a reenactment of childhood.

The goal is not to put mom on trial. The goal is to stop living in the same script.

And the moment siblings start speaking to each other directly, negotiating roles consciously, and telling the truth about what caregiving and history are stirring up, something shifts. Not because the past disappears, but because the present finally belongs to the adults in the room.