Randy Jackson, Journey bassist - watch video here
However, it's not like he was some kind of founding member. For two years, 1986 and 1987, Jackson was a session musician playing bass. A session musician is not a permanent member of a band - it's someone who is available to play at concerts or in studio sessions. He did also play on the album "Raised on Radio," which featured the hits "Girl Can't Help It" and "I'll Be Alright Without You."
It's still pretty cool, but let's not get crazy and act like he's John Paul Jones, Cliff Burton or John Entwistle. Below is the video of "Girl Can't Help It." Randy can be seen several times starting at around the 1:00 mark.