I think there are a lot of ways to interpret this song. I definetely feel like there's a third person involved. Maybe one of them has been cheating, or there's a child involved, like people have mentioned. My own theory is that the two people in the song are the ones having an affair behind someone else's back, or they had to hurt someone to be together. And now they can no longer forget or ignore that third person, and what they did to him/her is hanging over their relationship.
I think there are a lot of ways to interpret this song. I definetely feel like there's a third person involved. Maybe one of them has been cheating, or there's a child involved, like people have mentioned. My own theory is that the two people in the song are the ones having an affair behind someone else's back, or they had to hurt someone to be together. And now they can no longer forget or ignore that third person, and what they did to him/her is hanging over their relationship.
"There's no denying we feel the third one we do"