I can give you several Country Songs out now that basically follow a D to Em to G back to D chord pattern that sound the same, but aren’t.
The Everly Bros also would follow up a hit tune with another tune that was similar.
Creedence Clearwater’s John Fogerty had to take his case all the way to the supreme court. Rights to one of his early songs were bought by a record company who tried to legally prevent him from performing or writing any song in a similar style.
He won eventually after spending over a million legal dollars and not being able to perform his own music for many YEARS.
I recommend seeing him perfom live now if any chance arises.
http://en.wikipedia.org/wiki/Fogerty_v._Fantasy,_Inc.