Lily Allen and her sister, who is also her business partner, Sarah Owen admit they know "how to argue" and have been clashing heads for years. 

Luckily for the siblings, the fights are never detrimental to their relationship and take the occasional bickering as part of their bond.

Allen, who is due to be married this weekend to boyfriend Sam Cooper, told Irish show 'Xpose' that their company 'Lucy In Disguise' runs well despite their differences:

"It has its ups and downs. I think in any start up business it's stressful and that just gets multiplied by the fact that we know how to argue, we've been doing it for years but it's equally as rewarding when really good things happen because you feel like you're sharing it with somebody who understands. It's great."

Owen added that Allen "was not the little sister" she anticipated and found it challenging to accept her independent spirit:

"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."

Watch the sisters talk about their business here: