Three Dog Night's "My Old Kentucky Home (Turpentine and Dandelion Wine)"

I just listened to Three Dog Night's Seven Separate Fools.  I knew that part of "My Old Kentucky Home (Turpentine and Dandelion Wine)" sounded familiar (the line "oh, the sun shines bright on our old Kentucky home"), but I couldn't place it.  I looked it up on the internet and discovered that "My Old Kentucky Home" (which contains a similar line - "the sun shines bright in the old Kentucky home") is a song by Stephen Foster.  I found this interesting, but that's not how I knew that line.

Eventually though, I realized that it's also in the song "Here Comes Summer," which I have by both Cliff Richard and the Dave Clark Five.  It's slightly altered though, so there's no mention of Kentucky; it's just "oh, let the sun shine bright on my happy summer home."

Listening to the two lines of both songs back-to-back, they sounded similar, not only in the words, but also in the melodies.  I found the notation for Stephen Foster's "My Old Kentucky Home," and I'm fairly confident that both "My Old Kentucky Home (Turpentine and Dandelion Wine)," written by Randy Newman, and "Here Comes Summer," written by Jerry Keller, took Foster's melody (modifying it slightly) and at least some of his words.