EXCLUSIVE: Hilary & Haylie Duff's Advice to Kendall & Kylie Jenner on Navigating the Ups and Downs of Fame

Hilary and Haylie Duff are two of Hollywood’s most famous sisters – so it’s safe to say they know a thing or two about navigating the ups and downs of growing up in the spotlight.

Of course, Hilary, who turns 28 next month, shot to stardom on Lizzie McGuire in 2001. Haylie, 30, made a name for herself on the WB series 7th Heaven and starred in the cult classic, Napoleon Dynamite.

VIDEO:  Do Haylie and Hilary Duff Want More Kids?!

The pair, who shared the big screen in 2006’s Material Girls, understand people’s obsession over sisters in Hollywood – and in a new interview with ET – they shared some advice for another pair of siblings whose fame is only skyrocketing: Kendall and Kylie Jenner.

“I think one thing that was important for Hilary and I was always to be each other's number one support system and always be on each other's team,” said Haylie.

VIDEO: Kendall and Kylie Jenner Get Candid About The Price Of Fame 

Hilary echoed her sister’s sentiment, noting that growing up in the spotlight has its hardships.

“It makes life a little challenging when everyone watches everything you do,” she explained. “To have a support system from your sister and your sister be your number one fan and advocate is really important.”

Kylie, who just turned 18, opened up to ET earlier this year about how challenging fame can be for her.

But Hilary says she and Haylie have always been close.

“Being the younger sister, sometimes you get kicked to the curb, and she's always included me with her friends since the time we were little.”

And now, Hilary and Haylie are closer than ever – raising kids simultaneously and using their platform to put an end to “mom bullying.”

VIDEO: Kylie Jenner Reveals Her Biggest Social Media Regret 

Kendall and Kylie often share screen time together on Keeping Up With the Kardsashians – but will Haylie and Hilary ever reunite on the big or small screen? Both ladies are up for it!

When asked if we could see Haylie making a cameo on season 2 of Hilary’s TV Land sitcom, Younger, Hilary exclaimed, “Oh, that'd be fun!”

For more on Hilary and Haylie’s thoughts about working together in the future – check out the interview above. And, to see what they said about feeling criticized over their parenting skills check out the video below.

Hilary Duff On Being a First Time Mom: 'It's Really Kind Of A Lonely Place To Be'

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Follow Katie Krause on Twitter: @Katie_Krause