Kourtney Kardashian and Scott Disick
11/30/2011 at 12:00 PM EST
And baby makes four: Kourtney Kardashian
and longtime love
Scott Disick are expecting their second child.
"It's soooo exciting!" her sister Kim
tells PEOPLE. "They are so happy and so am I!"
Kourtney, 32, and Disick, 28, who have been together for four years – on a sometimes rocky road
involving their relationship – will also soon be celebrating son Mason Dash Disick
's birthday. He turns 2 on Dec. 14
As the Kourtney & Kim Take New York
star told PEOPLE
during her first pregnancy, "This baby was unexpected, but it's 100 percent a blessing."
Soon after Mason's arrival, Kourtney's younger sister, Khloé Kardashian, even remarked on what a change he brought to her sibling, Tweeting
: "Wow my sister has changed. She used to whip her boobs out for no reason. Now she does it to feed her child."