"My sister and I are best friends and we get along so well. She is so talented and inspiring to me. She's my role model." Says Hilary.

"Naturally, everyone thinks siblings would be jealous over each other and fighting, but my dad always said, 'If you ever fight over a part or cry over a part, you guys have to come home!'" Says Haylie.

The sisters currently live together in a huge mansion where they each practically have their own wing.

Hilary and Haylie promote Material Girls on TRL

They've done a number of duets including a cover of 'Material Girl' by Madonna (Did you know: Hilary and Haylie are the first musicians Madonna has EVER let cover one of her songs?) for their film 'Material Girls', a cover of the Go-go's 'Our Lips are Sealed' and the Disney classic 'The Siamese Cat song' from Lady and the Tramp.

"We're still a very tight-knit family, even though we live apart a lot. And now Haylie and I get to work together more and more. We're really close." Says Hilary.

They have or will appear in a number of films including this months release Material Girls, the upcoming animated films FoodFight and In Search of Santa and both girls first ever film True Women. They have both appeared on the shows Lizzie Mcguire, American Dreams and Joan of Arcadia.

Check out our gallery of Material Girls pictures Here

Though Hilary is arguably the most famous of the two Haylie has been rising in success recently. She matched Hilary's 'Choice Breakout Actress' win at the Teen Choice Awards in 2003 (for The Lizzie Mcguire Movie) by winning the award herself in 2005 (for Napolean Dynamite). Both girls are currently nominated in the Teen Choice Awards 2006.

Haylie has a number of films lined up including: I Remember, My Sexiest Year and Legacy and has just made her debut on Broadway in the musical 'HairSpray'.

"As a child I was shy. Haylie would be the one to go up and talk to people." Hilary said recently.

Check out our gallery of Material Girls pictures Here

It seems few people in Hollywood are as busy as Hilary Duff. She's been touring on and off for all of 2006 including concerts in South America, the UK, Australia, America and Canada. She'll soon be releasing her new clothing line for kids (Did you know: Hilary's company Stuff by Duff employs Robert Thorne, the manager that made the Olsen twins the multi-millionaires they are today) and a clothing line for dogs and then there's her third album out in November!

"It's crazy and so surreal. I feel like such a normal person, yet everybody around the world knows my music, my movie, my name and my face. It's crazy sometimes, but I'm so flattered. It's a good feeling." Says Hilary.

Check out our gallery of Material Girls pictures Here

As for Material Girls the film is out August 18th and stars Hilary and Haylie as Tanzie and Persia Marchetta both heiresses to their family's cosmetics fortune who are given a wake-up call when a scandal and ensuing investigation strip them of their wealth. The film also stars Angelica Houston.

Hilary recently said in her blog: "I can't begin to tell you how excited I am about the release of Material Girls on August 18th nationwide! I just saw the last cut of the movie and my sister Haylie is so good! She is funny and beautiful. You are going to see her in a different light than what you are used to seeing. Angelica Houston is elegant. I am truly happy and ecstatic over the final movie."