You are making it easy for your older sister to dominate you, Mariella Frostrup tells a woman in her 20s that she no longer needs to play by the old rules

The dilemma My older sister and I are both in our mid-20s but have never been close. From a young age she would show her strength, picking fights and, as we got older, these became more verbal. We have not been in each other’s lives much over the past 10 years, but what was normal teenage behaviour has transformed into a negative adult relationship. She seems to have a genuine dislike for me that I don’t want to put down to jealousy. That is so petty and I’m not sure what she would be jealous of. She makes me feel incredibly insecure. When I see her I have terrible anxiety and the things she’s called me (lazy and tight with money) are unfounded and mean. I get highly emotional and she doesn’t seem to care, switching from anger to cracking a joke minutes later. I recently spoke to my mother about this and she said she could see that my sister acts unfairly towards me, but she doesn’t want to get involved. I should also say that our father is currently undergoing cancer treatment which has put even more strain on our relationship, but I am trying to hold it together for our parents’ sake.

Mariella replies As you should. I’m sorry to hear about your dad and hope he makes a swift recovery. Sibling rivalry is as old as humanity itself, so your dilemma, while compelling, isn’t surprising or easily solved. It is, however, timely as the festivities approach and, along with the joy of reunions and gift giving, comes the less heart-warming prospect of immersion in family dynamics that haven’t changed since childhood.

The period around Christmas may be known as the season of goodwill, but there’s often scant evidence of it as old wounds are revealed to be as fresh as the day they were inflicted, and pecking orders created in infancy are re-established. So, while your dilemma may feel very specific to you, it’s actually pretty universal.

You can choose how to respond to the old triggers on display

It’s one of life’s great frustrations that the legacy of troubled relationships with siblings, who we spend only our formative years with, can survive far longer than the more positive aspects of family life. A fifth of our lives is the average time we remain with blood relations, but if allowed to flourish unfettered, it’s these relationships that can be the most defining and enduringly dysfunctional of our lives.

What your sister seems to have reflected back at you when you were small was a sense of your own inadequacy. Still, today, without needing to open her mouth, exposure to her pushes you right back to those vulnerable days of youth. That doesn’t mean there aren’t productive ways to deal with your on-going relationship.

I wonder if, as you wrote this letter, you had cause to wonder at the extent of the hurt you still consider her capable of causing you? I’m concerned it’s still triggering the same responses it did in the playroom. Does that strike you as dispiriting? Your early sense of inferiority and victimisation, partly (but certainly not exclusively) informed by your sister’s power play has continued way too long. You need to learn to extract yourself and build resilience, so your sister takes her sporting tendencies elsewhere. Getting on badly with siblings is more a nuisance than a life-threatening matter and in many cases is more easily dodged than resolved. You may not be able to choose your family, but you can definitely choose how much time you spend with them and how to respond to the emotional triggers on display.

So the question is why are you allowing this sibling rivalry to define your independent life? I can’t judge your sister’s behaviour because I only have it from one source, but it really isn’t something that need impact your psyche. Your sister sounds like a straight talker and possibly a bit of a bully, but when someone gives you the power to manipulate him or her it’s pretty irresistible and, in this case, she’s definitely still “got the power”.

Much as she is still enjoying unhealthy domination, you are making it ever so easy by continuing to display your vulnerabilities. You mention bringing it up with your mother and her reluctance to get involved. I’m not surprised. Separating your kids when they’re acting like infants is definitely a job you want to retire from as a parent once they’ve hit their 20s. My worry is you’re in danger of letting this dynamic define your adulthood instead of employing the resilience we all need to survive the rough and tumble. Until you develop a coping mechanism you’ll continue to be vulnerable.

Waiting for others to change their behaviour, investing in efforts to help them see the error of their ways and even expecting justice to be served, are all empty expectations. The only person you can work on is yourself and until you have a better picture of who you are, your sister will continue to assert herself. There are plenty of professional therapists who can help with this issue, or you can resolve to evolve from playground patterns under your own steam. If so, breathing and counting to 10 before you react, particularly over Christmas, is an indispensable tool!

If you have a dilemma, send a brief email to mariella.frostrup@observer.co.uk. Follow her on Twitter @mariellaf1