Rob Kardashian Stepdaddy Material For Bday Party with Blac Chyna's Kid

3/17/2016 8:16 AM PDT

Rob Kardashian: Stepdaddy Material ... Birthday Party with Blac Chyna's Kid


Rob Kardashian kicked off his 29th birthday celebration in stepdad mode -- hanging with Blac Chyna and her son, King Cairo.  

The trio was all over LEGOLAND on Wednesday, looking like a happy family and having a blast. Rob even wore something besides a black tee for the first time since he's returned to the spotlight.

He's knocking the door on 30 today, but Rob's still a kid at heart. Theme parks'll do that to you.