Khloe Kardashian has revealed that she is also "beyond thrilled" that sister Kourtney is pregnant with her second child.
Despite having unsuccessfully tried for a baby with her husband Lamar Odom since their wedding in 2009, Khloe has claimed that she is "overjoyed" at Kourtney and her boyfriend Scott Disick's news.
Kourtney announced that she is nine-weeks pregnant, and is excited about having a brother or sister for her 23-month-old son Mason.
Writing on her official blog, 27-year-old Khloe said: "I am BEYOND thrilled to fiiiiinally be able to share with all of you the fabulous news that my beautiful big sister Kourtney is expecting yet again! Can you believe it?! Masey is going to be a big brother!"
Khloe continued: "We are all so overjoyed by this wonderful news and are counting down the minutes until we get to meet the newest member of our family.
"Kourtney is the greatest mum in the world and I am so proud of the woman she has become. I can't wait to see her with a kid in each arm! She'll be a pro. LOL. And if this next baby is anything like Mason, then we will truly be the luckiest family in the world."
Kourtney found out that she was pregnant at four weeks and woke up boyfriend Scott at 7am with the news.
In an interview with Us Weekly, Kourtney said: "Scott and I are so excited to announce that we are expecting our second child and are thrilled to be expanding the love in our family."
Kim Kardashian also wrote about the couple's amazing news.
Kourtney and Mason....