Notice how there is no drums in this song. Jack did this song alone on the piano without Meg. These means a lot. Jack has referred to Meg as his sister. They were married, and now they have "split up," Jack has a longing, so to speak, to be with Meg again. Because of their current relationship, Jack sees everybody in Meg's life, and is jealous and lonely, even if Jack is with somebody, as he currently is. It shows Jack's love for Meg.
Notice how there is no drums in this song. Jack did this song alone on the piano without Meg. These means a lot. Jack has referred to Meg as his sister. They were married, and now they have "split up," Jack has a longing, so to speak, to be with Meg again. Because of their current relationship, Jack sees everybody in Meg's life, and is jealous and lonely, even if Jack is with somebody, as he currently is. It shows Jack's love for Meg.