Regina and Killian may both be “emotionally damaged” from tragically losing people they loved, but then again, so are Baelfire and Emma scarred from feelings of abandonment. It doesn’t mean they wouldn’t be good together in the long run. Rather than preventing people from moving on, sometimes it helps if two people have common experiences; in losing love and rediscovering it in one another, it could actually help them move on in a healthy, positive way. I could see it happening if Regina realizes evil doesn’t satisfy her need for love and family and likewise Killian realizes that revenge doesn’t make up for losing Milha.
"That’s how you know you’ve really got a home. When you leave it, there’s this feeling that you can’t shake. You just miss it." Neal Cassidy