Lily Allen believes her music success caused problems between her and her older sister Sarah Owen.
The 'Not Fair' singer was never close to Sarah - who shares the same mother, Alison, as Lily - growing up and their rift deepened as they got older.
Lily believes a "personality clash" caused by her pop career and the success of their actor younger brother Alfie put a huge strain on their relationship .
The 25-year-old star - who is pregnant with her first baby with her boyfriend Sam Cooper - said: "It was a very difficult time and there was a big personality clash. I think it was really tough for Sarah to see her little sister and brother doing so well."
Sarah, 30, admits Lily was never the "adoring sister" whom she had expected, and blames the five year age gap between them for their differences.
She told Stylist magazine: "I've spent a lot of time feeling frustrated because I'm not particularly amazing at any one thing.
"I think Lily was angry at me for a lot of the stuff that happened in our childhood. I'm five years older so I was having my whole teenage experience just as Lily was forming her opinions.
"She was not the little sister I expected at all. When mum was pregnant I thought I was going to have an adoring sister who wanted to be guided by me.
"But it became clear really early on that Lily was a fiercely independent spirit who would take guidance from no one."
The pair have since settled their differences and are now partners in London vintage clothing shop Lucy In Disguise.