Instagram's most popular model Jen Selter is a fitness superstar- and it runs in the family.

Jen Selter Flaunts Her Giant Hump As She Rests Comfortably

On Sunday- which is also apparently National Sister Day- Selter took to her page to post a new photo of herself with her sis named Steph. The two stand near a pool wearing strapless and colorful bikinis in a side shot.

For the most part, the girls look very much alike with their long dark hair and athletic bodies. Steph has a petite yet strong torso with muscular legs just like her sister. Her backside isn't quite as iconic as Jen's, but that might change with practice.

 #nationalsisterday love you peanut @stephselter

A photo posted by Jen Selter (@jenselter) on Aug 2, 2015 at 8:42pm PDT

Jen Selter Reveals What She Goes 'To Bed' With

Jen's Instagram success is continuing to take charges as she hits close to seven million followers. Now that she's a big star, her sibling is becoming big with more than 40,000 followers on her page.

Based on the way Jen flaunts her curves, it's no mystery why she became a celebrity.

 All white everythang⚪️ #HappyFriday

A photo posted by Jen Selter (@jenselter) on Jul 31, 2015 at 3:04pm PDT

Earlier this year, the model spoke to Black Book on how proud she is of herself for making it this far.

"I have worked hard and now I'm able to share my passion and motivate others to also live a fulfilling and healthy life," she said. "Anything is possible when you push yourself to achieve your goals."

Tags: Jen Selter