It's Jeffrey Dean Morgan and Hilarie Burton!
Jeffrey Dean Morgan — who played Denny Duquette, Izzie's (Katherine Heigl) gone-too-soon husband — and Hilarie Burton — who played Dr. Lauren Boswell, Arizona's (Jessica Capshaw) fling — started dating in 2009 and welcomed son Augustus in March 2010.
The connection gets weirder. After Denny died, Izzie started dating George (T.R. Knight), i.e. Callie's (Sara Ramirez) husband at the time. And Callie's second spouse is Arizona, Lauren's one-stormy-night-stand.
In other words: Jeffrey plays Denny, who loved Izzie, who loved George, who was married to Callie, who loves Arizona, who slept with Lauren, played by Hilarie.
What a tangled web Grey's weaves!