Cristina and Owen have finally come to a comfortable place in their relationship on Grey's Anatomy - which naturally means it may be time for another shakeup.The couple has certainly seen some rough times over the past few seasons, but following their divorce, Cristina (Sandra Oh) and Owen (Kevin McKidd) decided to keep things simple by not defining their relationship. Remarkably, that has seemed to work from them thus far. "I don't know if it's better for them, but they're in the midst of believing that," executive producer Shonda Rhimes tells TVGuide.com. "They're not talking about it and not defining it so they don't have to talk about all the reasons why it didn't work in the first place."Grey's Anatomy: Do Cristina and Owen belong together?One of the main reasons the relationship didn't work was that Cristina has always adamantly been against being a mother, something Owen thought he could get on board with. But his want for a family ultimately was the fracture that caused the demise of their relationship. "I am defiantly in support of a character's right to not want children," Rhimes says. "As much as I love kids, I feel like it's very intriguing to me to have a character who absolutely does not want children and is not interested in having them and isn't going to suddenly melt the minute a baby is placed in her arms. That's not Cristina. What that means for a guy like Owen, who was made to nurture, is going to be really interesting."Of course, not addressing their problems could ultimately be the couple's downfall this time around. "Right now they're having a wonderful time and they're in love because they don't have to ask any of those questions," Rhimes says. "The divorce freed them from having to ask any of those questions, but those questions are going to come up again for them and we're going to watch them struggle to stay in love through those questions."Mega Buzz: Who's breaking up on Grey's Anatomy?But Rhimes promises that Grey's will not just be retreading on the same storyline that lead to Cristina and Owen's initial breakup. "They have to go about it in a different way," she says. "Hopefully they have a different perspective on things now. They have a perspective on time. They understand what their lives were like without one another. Obviously neither one of them is interested in that. I think they have a different way of looking at things now. They've been through a plane crash, so they have a different perspective on life. They have to be looking at this differently."Do you hope Cristina and Owen can figure things out?Grey's Anatomy airs Thursdays at 9/8c on ABC.