11/22/2011 AT 4:00 PM ET
“Doing this show has really changed Rob,” Kim, 31, a former Dancing contestant, tells Celebuzz. “He s really grown up so much and it s been incredible to watch him each week.
As a tuxedo-clad Kim joined sister Khloé and mom Kris Jenner in the ballroom on Monday, Rob, 24, scored his first perfect 30 for a daring freestyle dance in which he lifted and twirled pro partner Cheryl Burke.
We were all so blown away by Rob s performances last night,” says Kim. “Each week he works so hard and is always prepared, but [we] never knew he would get a perfect score!! We were all amazed and so happy! Rob is so excited to have made it this far and I am so proud of him.”
Rob became an unlikely frontrunner, pulling ahead of favorites J.R. Martinez and Ricki Lake in the race for the mirror-ball trophy, which will be handed out on Tuesday’s show.