On the original series, Charlene recurred as J.R. Ewing's promiscuous niece from 1978-90, while Steve's ranch hand character (who was revealed to be J.R.'s half brother) appeared from 1978-1991. Steve last played Ray in the 1998 Dallas reunion movie, War of the Ewings.
So why is J.R. (Larry Hagman, who will appear in the pilot) not listed as attending this family function? Well, that we'll have to wait and see when and if TNT orders Dallas to series. (Please TNT, order Dallas to series!)