"There was no spark. What's interesting is, there was never anything. It wasn't until we were well into the dissipation of our respective relationships. Going through something so difficult at the same time, we became very good friends. We became closer and closer," Contactmusic quoted Swank as telling Britain's Hello! Magazine.
"It was so unexpected. We both recognised that if we were going to take the relationship to the next step, we could no longer work together," she added.
While the 35-year-old star has no intention of marrying John, 41, in the near future, she hopes to start a family with him one day. She even enjoys spending time with his son Sam, from a previous relationship.
"Sam's a sweetheart. I most definitely want children. It's something I'd like to do someday. And when the timing is right I'll hopefully know it," she said.