Still Fighting Over the Remote at 40: The Truth About Adult Sibling Rivalry

At every family Christmas for the past decade, Karen, 47, from Leeds, and her younger brother Steven, 43, have found a way to fall out before the turkey is even carved. "Last year it was who forgot to invite whom to a barbecue in June," Karen sighs. "We're grown adults arguing like we're ten and eight again, fighting over who got the bigger slice of cake."

Sibling rivalry is often assumed to be a childhood phase, something outgrown along with school uniforms and bedtime stories. But according to family therapist Dr Owen Blackwood, unresolved rivalries frequently persist, and even intensify, well into middle age. "The patterns we establish with siblings in childhood are some of the most deeply grooved in our entire emotional lives, because they're formed before we have the tools to process them properly. Add the pressures of ageing parents, inheritance and old wounds, and adulthood can actually reignite rivalry rather than ending it."

For many families, the flashpoint is caring for elderly parents. "That's when it really kicked off for us," says Karen. "Mum needed more support, and suddenly it was like being back in the playground, him accusing me of always being the favourite, me accusing him of never lifting a finger."

Dr Blackwood says this dynamic, sometimes called "caregiver rivalry", is one of the most common issues he sees in adult sibling counselling. "One sibling often takes on more practical caregiving, while another may contribute financially or emotionally from a distance. Both feel unappreciated, and old childhood narratives, 'you were always mum's favourite', resurface almost instantly."

Inheritance, unsurprisingly, is another major trigger. "I've seen siblings who hadn't spoken in fifteen years suddenly locked in legal disputes over a set of dining chairs," says solicitor Priti Anand, who specialises in contested wills. "It's rarely actually about the object. It's about decades of feeling unequal in the family, finally coming to a head."

Not all adult sibling conflict is dramatic. For Debbie, 39, from Norwich, and her sister Amy, 36, it's more a low hum of competitiveness that's never fully resolved. "Whose kids are doing better at school, whose husband earns more, whose house is bigger. It's exhausting, and I hate that I still care, but I do."

Psychologist Dr Halima Osei, who researches family dynamics, explains that this competitive streak often stems from early comparisons made, sometimes unintentionally, by parents. "Even throwaway comments like 'why can't you be more like your sister' can plant comparison seeds that grow for decades. As adults, siblings unconsciously keep score, even when they consciously know it's pointless."