elizabeth olsen
Can you see the resemblance?When news broke that Mary-Kate and Ashley Olsen's sister, Elizabeth Olsen, was going to star in the new independent flick, Martha Marcy May Marlene, with Hugh Dancy (Claire Danes’ husband), this was the question on everyone's mind:

The Olsen twins have a sister?

Apparently so. (And a brother, too!) She's three years younger, a student at NYU, and has actually acted in other movies. But you wouldn't know it because her other two siblings are usually hogging the spotlight.

In fact, here are four other celebrities with "secret" siblings in the shadows.

 

 

 

 

Does the woman on the right look at least a little familiar? That's Casey Patridge -- sister to new Dancing With the Stars cast member Audrina Patridge -- and you might have seen her guest star a few times on The Hills.

audrina casey patridge

 

If you've ever wished that James Franco had a brother, today is your lucky day -- he does! Dave Franco, the younger of the two, has appeared in Scrubs and Charlie St. Cloud. Let's hope we see more this guy soon!

Dave Franco

 

Turns out Inception star Joseph Gordon-Levitt has a dread-locked, fire-dancing brother named Dan. The jury's still out if Dan qualifies as a nerdy-sexy guy like his hottie bro.

dan gordon-levitt

 

Awwww ... Jon Heder not only has a brother, he has a twin brother! Meet Daniel.

jon daniel heder

Which celebrity siblings are your favorite?

 

Images via Getty; Flow Temple; Splashnews.com; Getty