Kourtney Kardashian says she was a mean big sister

Kourtney Kardashian poses at the launch of Kardashian Beauty at ULTA on Sunday, June 9, 2013 in Huntington Beach, Calif. (Richard Shotwell/Invision/AP)

Kourtney Kardashian admits she was mean to younger sister Kim Kardashian when they were kids.

The 34-year-old reality TV star was always bossy towards her sibling, who is 18 months her junior, when they were younger and didn't even appreciate it when her sister threw her a surprise birthday party.

Kardashian said: "When we were growing up, I could boss Kim around! Once she threw me this party with all my friends at a house in Palm Springs and when I got there everyone was like: 'Surprise!' and I was such a little b***h to Kim.

"The whole weekend I was really mean to her. I was such a bossy older sister!"

The brunette beauty - who has children Mason, four, and Penelope, 18 months, with partner Scott Disick - gets on much better with her sister these days, though they still row about clothes.

She told Now magazine: "It's so stupid and catty I know, but we've done it our whole lives. We're only 18 months apart, so we've always shared our clothes. It caused so many fights growing up. Thank God we don't wear the same size shoe!"

Though she is the eldest in the family, Kardashian admits her 29-year-old sister Khloe Kardashian acts like the most responsible.

She said: "Now I think I sometimes play the younger sister, while Khloe plays the eldest.

"With Khloe, a lot of the times she'll try to act like she has it all going on and she's so tough.

"Sometimes when we travel together, she's like: 'Come on, little girl,' and she talks to me like I'm six. It's really funny. We all kind of have our roles - it's cool."