Kevin Siembieda (born January 2, 1956) is an American game designer and artist who co-founded Palladium Books in 1981 with Erick Wujcik.
From the Traveller RPG wiki on wikia.com:
In 1979, Kevin Siembieda was a freelance artists working for Judges Guild and producing art for their Traveller and Dungeons and Dragons products.
In 1980 Kevin founded Palladium books and published the Palladium Fantasy, which was the beginning of the RIFTS game system. Kevin still runs Palladium games, writing the various books and supplements and producing art.