Nicole Richie is engaged to her long-term boyfriend Joel Madden, the starlet revealed last night. The couple got together in December 2006 and have two children together, Harlow, 2 and 5-month-old Sparrow. Nicole broke the news on The Late Show with David Letterman last night and fiance Joel then Tweeted to say, "Yep. I'm engaged. Very happy. We've been engaged for a while, so your [sic] all kind of late on that. But thanks for the hooplah all the same." Nicole is thrilled to be getting married and the pair hope to tie the knot this summer. Congratulations guys!