Kate, Charlotte, George and William in March 2016.
"I think they both would have been overwhelmed at the thought of a third child a year ago,” the insider added. “But now it sounds perfect. They've both always wanted a big family."
Kate and William — who married in a lavish wedding in April 2011 — are already parents to kids Prince George, 3, and Princess Charlotte, 1. Looks like the world will be on royal baby bump watch yet again in the coming months — can't wait!
Click through the gallery below to see George and Charlotte’s cutest photos!