Chris posted this Monday AM ... "Sweet Katherine, so happy you said yes! I'm thrilled to be marrying you. Proud to live boldly in faith with you. Here we go!"
All the signs have been there for a few months ... he's been hanging with her entire fam, including Arnold Schwarzenegger and Maria Shriver. Chris, Katherine, Maria and Patrick Schwarzenegger were all just in Mexico together.
No word on when they're tying the knot.
So, Chris is going to become part of the Kennedy klan. Maria's mom, Eunice Kennedy Shriver, was the sister of President John F. Kennedy, Robert Kennedy and Ted Kennedy.