Kim Kardashian's nephew is jealous of her three-month-old daughter, North West.

The 'Keeping Up with the Kardashians' star's sister Kourtney Kardashian admits her three-year-old son, Mason, with her boyfriend Scott Disick, is still adjusting to the new member of their family.

The 34-year-old star told People.com: ''He gets a little jealous because he and Kim were so close. He doesn't understand because he's not the big center of attention.''

Kourtney said that Kim is still learning how to cope with children and doesn't know what to say to make Mason feel better.

She said: ''I don't think [Kim] knows what to do; she's just like, 'You don't like me anymore?' She feels like he ... is getting older and changing, and I think she gets confused and doesn't know how to handle it. He's like, 'Why don't you like me anymore?' because he sees her with the baby.''

But Kourtney's daughter Penelope, 14 months, is a huge fan of North, whose father is Kanye West, and is in ''awe'' of her younger cousin.

She said: ''Whenever [Penelope] sees [North] -- the second she walks into the room, Penelope gets so excited.''