Kim Kardashian chose to celebrate Rob's birthday with a throwback photo.
Kim wore a tight-fit, sparkly dress and can be seen holding on to her brother, who is sporting a suit, minus the jacket and a "Happy New Year" decoration on his head.
"Happy Birthday to my brother Rob!! I love you so much and wish you all the happiness in the world! I love raising our kids together, you're the best dad and friend! Can't wait to celebrate today!!" Kim wrote on the caption accompanied by two clover emojis referencing St. Patrick's Day.
Many of Kardashian's family members wished the 31-year-old a happy birthday, including Kris Jenner and Kendall Jenner.
"Happy birthday [Rob Kardashian]!! You are the most wonderful son a mom could ever ask for and I thank God for you every day! It brings me so much joy to see the incredible father you have become. I am so proud of you!! Love, Mommy," Kris Jenner wrote in the caption of a collage of photos of the two.
"Birthday Boy Bobby," Kendall Jenner wrote, posting a photo of the two as children.
Sister, Kourtney Kardashian also posted a photo of a giant balloon display reading the words "Happy Birthday Rob."
A surprising birthday wish came from his ex Blac Chyna, who the reality star is currently in the midst of a legal battle with.
"Happy Birthday Rob from Dreamy and Chy," Chyna wrote in her Instagram story Saturday, posting a throwback photo of the three of them together at a movie theater.
Chyna and Kardashian started dating in 2016, and welcomed daughter Dream Nov. 10 of the the same year. The two broke up in December, quickly got back together, then broke up again in February 2017.0comments
Kardashian infamously went on a social media tirade against Chyna in July 2017, accusing her of cheating on him with multiple men and posting sexually explicit photos of her online.
This led to Chyna filing a restraining order against Kardashian, but the two managed to mend their relationship and agreed to settle their custody agreement over Dream by deciding to co-parent her.