The reality star couldn't be prouder of the 24-year-old for reaching the final three, and said that the show has helped him mature.
'Each week he works so hard and is always prepared, but never knew he would get a perfect score,' she told Celebuzz of his Monday night freestyle performance. 'We were all amazed and so happy. Rob is so excited to have made it this far and I am so proud of him.
'Doing this show has really changed Rob. He's really grown up so much and it's been incredible to watch him each week.'
And their sister Khloe, 27, echoed Kim's sentiments.
'By the time last night's show was over my voice was seriously gone! We just couldn't stop screaming after Rob’s freestyle,' she said. 'Watching Rob improve week after week has been so special for my entire family. His dedication is truly beautiful. We're all just so proud of him!'