The Tv couple will reunite for a Ewing family reunion storyline, set for next spring (13).
Gary and Valene are the parents of Lucy Ewing, who has been portrayed on Tv by Charlene Tilton since the late 1970s.
Shackelford and Van Ark last appeared in an episode of Dallas when their characters were featured in the show's 1991 finale.
Knots Landing ran from 1979 to 1993. The new Dallas returns to U.S. Tv screens in January (13) after a successful first season run.