I have three daughters: a set of twins and their younger sister, all in their 20s. The older girls have been feuding since 5th grade. As a child and teen, Twin A was outgoing, popular and athletic; while Twin B was less confident socially, not gifted athletically and emotionally volatile. In retrospect, we probably should have had them in different schools, because Twin A felt resentful of Twin B’s dependence, and Twin B grew angry at her perceived shortcomings. Our younger daughter is closer to Twin B, which causes a piled-upon feeling in Twin A.

Now successfully launched adults with lovely long-term boyfriends, they both still feel wronged by the other, which makes family gatherings a minefield. I am trying to let them solve their problem, since any time I try to help it escalates the situation. How do I navigate going forward through all the happy family events (weddings, babies, grad-degree celebrations) without their ongoing conflict derailing me?

From the Therapist: It’s so hard to watch your children struggle to get along and then carry those conflicts into adulthood. Most parents hope their children will outgrow their differences and find a way to connect as they age, but the challenge for many siblings in moving forward is that they often don’t understand what their feud is really about.

Implicitly or explicitly, we’re all given roles in our families — the generous one, the selfish one, the rigid one, the flexible one, the easygoing one, the difficult one. Sometimes these roles are named out loud (“Jane’s the smart one, she’ll go to an Ivy League school” or “Sophia’s the sensitive one, she overreacts”). Sometimes they’re couched in complaints: “Why can’t you just let things roll off your back like your sister?” And sometimes parents’ own unexamined anxieties and insecurities turn a child’s normal temperament into something that needs to be fixed: “Don’t you want to be more social?” to the introspective daughter who prefers reading at home on a Saturday night to going to loud parties like her sibling.

The more these roles are reinforced — by parents, peers, teachers and the siblings themselves — the more entrenched they become. This happens at a time when children are forming their identities (you say the conflict was particularly noticeable starting in 5th grade), and for many siblings, what looks like conflict is partly an ongoing fight for separate identities. But since twins go through their developmental phases in parallel, the struggle can be heightened: Who am I if I’m not compared to you? Your twins didn’t just grow up as siblings; they grew up as both mirrors and contrasts.