We have another Prentice which has nothing to do with Jackie's dad. As with Grandma Connolly, shouldn't this be Grandad Prentice? "Prentice" comes from Jackie's maiden name after all. Otherwise then Prentice (Army of Ghosts).
Talk about it here.
"Granddad Prentice" was the father of Jackie Tyler and the grandfather of Rose Tyler. He smoked. He died from a heart attack in 1997, but according to Jackie in 2007, came back as a friendly ghost. This ghost was actually a Cyberman that was passing through the Void to reach Rose and Jackie's universe. (TV: Army of Ghosts)