Is this the siblings' battle of the century? Rob Kardashian may apparently be starting a fight with his sister Kim K, and he surely knows how to attack the latter in a manner that would crush her ego.

Over the weekend, Kris Jenner's only son took to Instagram to diss Kanye West's wife by comparing her to Rosamond Pike's role in "Gone Girl."

Apart from comparing Kim K to Amy Dunne, Rob also threw major shade at baby North's mom by calling her a b***h.

Rob Kardashian's Instagram post is a snap of Amy Dunne covered in blood. And he proudly captioned the disturbing photo: "This is my sister Kim, the b**ch from Gone Girl."

 This is my sister kim , the bitch from Gone Girl,,,

A photo posted by ROBERT KARDASHIAN (@robkardashian) on Mar 22, 2015 at 10:38am PDT

Well, it is pretty obvious that there is bad blood between Rob and Kim. For one, the "Dancing With the Stars" Season 13 alum does not usually post anything about his sisters and family on social media if it's not a big deal.

Besides, he is completely out of the limelight that his family is basking under after he bowed out from Kim K's wedding with Kanye West in Italy last minute, Daily Mail has learned.

The 28-year-old reality star has since been absent on their family show "Keeping Up With the Kardashians." Not only that, he was also cut out of the picture since producers of the show decided not to develop a storyline for him on the E! show.

Rob has also cut his ties with his family online after he un-followed every single one of them on Instagram, reports TMZ.

As of late, it is still unknown what prompted Rob Kardashian to slam Kim K like that. Whether he was just joking or not is yet to be known.

Meanwhile, it seems that Kim has yet to learn about what his brother did to him. She still hasn't responded to Rob's not-so-pleasant post.

But it's good that she has her family to keep her busy. The controversial reality star recently shared a snap of her husband and their daughter playing together at the beach. She even captioned it with: "Beach Day #AllDay."