Credit: Jackson Lee/; Jason LaVeris/FilmMagic

Kourtney Kardashian is a reality star, fashion empress and author.

But the role she takes most seriously? Being a mom to 2-year-old Mason.

"[Some] people may think [badly] of Kourtney, but she is the best mother," Rob told Us Weekly Wednesday at the Duracell presents Daughtry concert in NYC.

What makes Kourtney such a wonderful parent? "Her morals," Rob said. "My dad has taught her a lot, even with money. She doesn't go and spoil [Mason]. He has a really good upbringing and strong morals, and he's just surrounded by so much love. Everybody just gives him so much love. He's spoiled in that sense."

Mason's very proud uncle gushed that the tot is "so good, and he never cries."

"I swear he is so smart," he added. "I am not being biased, but he's the cutest kid. He's the best. He's the best-behaved!"

Rob is hoping Kourtney and Scott Disick's baby-to-be will be a boy. "I think it would be kind of cool to have two brothers," he told Us. "We've never had that in the family!"

Rob also let Us in on a holiday secret. "I'm going to be Santa Claus this year for Mason," he said. "I'm helping get all of the presents together while he's asleep... I'm Santa's helper. That's a good way to put it."