I always thought that "Heart of My Heart" was a song about a gang that sang a song that maybe didn't exist. But that Excellent Song Sleuth, Jim Dixon, found the original lyrics for THE GANG THAT SANG "HEART OF MY HEART" and THE STORY OF THE ROSE (a.k.a. HEART OF MY HEART). And now that I think of it, I am familiar with the original song. No, wait...."Peg o' My Heart" is the one I know.
You'll find the lyrics in this thread (click).

-Joe-