Kurt Russell is not only playing Star-Lord’s father, but also the living planet EGO. Yes, Jack Burton is going to be a planet and a father. Footage shown during Marvel Studios Hall H presentation at Comic-Con confirmed it.
Sylvester Stallone is also in the film, but his role is unknown at this point. Taserface (Chris Sullivan) and his band of ravagers will also make an appearance in the film.
You can get more details about the living planet.. Ego from Wikia.