There is nothing like the bond of sisters and Nicole Richie's birthday post to her younger sister, Sofia Richie Grainge, proved that the two are as close as ever. On Thursday, the Simple Life alum shared a silly video to her Instagram Story that can only be described as two sisters acting like, well, sisters.

In the clip Sofia, who wears a very chic stealth wealth (she's practically the inventor of the trend, after all) leather blazer, walks funnily over to her older sibling who is holding a pink balloon tied to a white string. Sofia starts head banging while Nicole begins hitting her over the head with the ballon. Sofia continues jumping around while laughing at their silly behavior.

In the next slide, Nicole posted the sweetest throwback of the two that captures a tiny Sofia perched on her big sis's back. Sofia holds onto Nicole's necklace and Nicole, who wears a cream-colored tank top and brown-and-white striped trousers, wraps her arms around Sofia's legs.

"I love you @sofiarichiegrainge," she simply captioned the snap.

The sister duo's dad and famed singer Lionel Richie also shared a couple of baby photos in honor of Sofia's 25th birthday. In one photo, a toddler Sofia sits at a table with her arms crossed. Lionel captioned the Story, "Today is the day" with a cake and laughing face emoji before tagging his youngest daughter. The next photo shows Sofia sitting on her dad's lap with braids in her hair and a smile on her face.

On Wednesday, Sofia celebrated her birthday eve with a cute couple selfie alongside her husband Elliot Grainge, which she captioned the hands-in-a-heart-shape emoji.