The question isn't who was first, but who REGISTERED it first. From what I can see, the first registration of Kiss FM was in 1996 by Clear Channel Communications. Actually the first registration was Citicasters, which was bought by Clear Channel.
Clear Channel also registered Planet Kiss 102.3, but that trademark is now listed as dead. That might relate to the iHeart station in Albany.
Heftel Corporation of Chicago registered Kiss Radio in 1988. But that's a separate trademark.
WKYS used the lips in their logo but NBC apparently never trademarked it.