Sibling rivalry is a natural part of family life. But healthy competition gets taken up a notch when your sisters and brothers are famous! This year, a few stars rose to fame -- and outshined their already-famous siblings!

We saw Chris Hemsworth (big bro to Miley Cyrus' BF Liam Hemsworth) rise to fame as Thor, Kendall and Kylie Jenner (the youngest of the Kardashian sisters) following in their sisters fashionista footsteps, and Pippa Middleton (little sis to Catherine Middleton, aka the Duchess of Cambridge) steal her sister's royal wedding day spotlight.

Here's a breakdown of 2011 top breakout siblings:

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1. Elizabeth Olsen: The younger sister of Mary-Kate and Ashley Olsen. Up until this year, Elizabeth's career consisted of some theater work, a few appearances in her sister's projects and spots on various TV series like Made In Hollywood. But in 2011, Elizabeth made waves with her riveting performance in the haunting indie Martha Marcy May Marlene. She's even getting Oscar buzz for her work in the film. She also starred in two other indies this year, Silent House and Peace, Love & Misunderstanding. Umm, someone needs to bottle and sell the Olsen DNA.

2. Chris Hemsworth: Big brother of movie star/Aussie hunk/boyfriend of Miley Cyrus, Liam Hemsworth. This Australian-born actor has been trying to break into Hollywood since 2002 when he began his acting career as King Arthur in the TV series Guinevere Jones. He continued on as a TV actor for 5 years, landing a recurring role for 3 years on the Australian soap Home and Away, before getting his big break in 2011. Chris landed the lead role of Thor in the movie Thor, a role he will reprise in 2012 in The Avengers. He was pretty phenomenal, but let's just say his pectorals stole the show. The now famous actor has a total of 5 projects in the works for 2012, including playing opposite Kristen Stewart in Snow White and the Huntsman.

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3. Elle Fanning: Dakota Fanning's little mini-me. As the younger sister of an already accomplished actress, Elle stared her acting career even earlier than Dakota: at 2 years and 11 months. Her first role was as the younger version of Dakota in I Am Sam. A year later, Elle played a younger version of her sisters role again in Taken. While playing the younger version of her sis could be a career in and of itself, she started playing her own roles, with appearances on CSI, House M.D., Law & Order SVU and Dirty Sexy Money. Last year, she starred in Sofia Coppola's indie Somewhere. And now, in 2011, Elle landed the breakout role of Alice Dainard in the blockbuster flick Super 8 -- and then followed up with V in Twixt and Lily Miska in We Bought a Zoo, which also stars actor Matt Damon. At only 13-years-old, we imagine her list of credits will be as long as Meryl Streep's by the time she graduates college.

4. Nash Overstreet: Nash has been living in the shadows of his famous brother Chord Overstreet ever since Glee took over our airways, but not anymore. This lead guitarist had the year of a lifetime with his band Hot Chelle Rae. Hot Chelle Rae was relatively unknown until their hit song Tonight Tonight went double platinum in 2011.

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5. & 6. Kendall & Kylie Jenner: Kendall and Kylie Jenner were already known as the younger sisters of Kim, Khloe and Kourtney Kardashain, but in 2011 these teenage reality stars set out to make a name for themselves...And they did just that. Best known for the reality series Keeping Up with the Kardashian's, these two teen fashionistas created their own web series on YouTube, Keeping Up with Kendall & Kylie, a show that has gained its own dedicated fanbase. Although they have had great success with reality TV, fashion is their passion and both Kendall and Kylie have begun careers in modeling. The two teens were recently named "Brand Ambassadors" for Seventeen magazine. And did we mention they're still in high school??

7. Dave Franco: Following in the footsteps of older brother James Franco, Dave has been busy pursuing a career in acting. Named one of the Breakout Stars to Watch in 2011 by MTV's NextMovie.com, Dave has stolen his big bros spotlight with the role of Mark in Fright Night, alongside Colin Farrell and Anton Yelchin in the 2011 3D comedy horror. Next up? Dave stars in the big-screen adaptation of 21 Jump Street as well as the buzzed-about zombie flick Warm Bodies.

8. Pippa Middleton: By far the biggest spotlight stealer of 2011! Pippa shot to fame for being the hot sister of the Duchess of Cambridge, Catherine Middleton. No one had even heard of Pippa until she stole the thunder from her big sis on her wedding day. Pippa showed up to the wedding of the century (Prince William & Catherine Middleton's Royal Wedding), in a form-fitting white dress that made boys the world over drool. Headlines around the globe read 'Pippa Middleton Steals the Show,' 'Pippa Middleton Outshines Sister at Royal Wedding,' Pippa Middleton 'Hotter' than Kate.' Even now, months later, Pippa gets just as much, if not more media attention than her Royal sibling. In fact, there are certain fan clubs dedicated solely to Pippa's, ahem, posterior.

Who is your favorite famous sibling of the bunch??

Photos courtesy of Fame Pictures