"Happy Birthday, Robbbbbbbb !!!" Chyna captioned a bizarre video of Kardashian as Batman.
The reality star donned the superhero costume thanks to Snapchat's new Batman vs. Superman feature, laughing as lightning crashed around him.
The pair enjoyed a fun excursion the day before Kardashian's birthday, taking Chyna's son, King Cairo, to Legoland and posing for a series of cute photos together.
And Chyna wasn't the only one to wish the sole male Kardashian a happy birthday. Momager Kris Jenner posted a photo of her son to Instagram, writing, "God blessed me beyond measure the day you were born. You are the most amazing man who is kind, funny, smart and you have the best heart. You are beautiful inside and out and have brought so much joy into my life. Thank you for being the best son a Mom could ever dream of…I love you soooo much @robkardashian and I'm so proud of you."
Despite rumors of family tension between Kylie Jenner and Rob -- due to Rob dating the ex of Kylie's current boyfriend, Tyga -- Kylie posted her own birthday message for her brother.
Sharing a throwback photo of the two dancing, Kylie wrote, "Happy Saint Patrick's Day & Happy Birthday Bobert."