It's traditional for families to go to shows together this time of year. Less common is for families to perform in shows together. But there are no less than three parent-child duos in Theatre IV's "King Island Christmas," the company's holiday musical that opened at the Empire Theater downtown last Friday. Take into account Theatre IV's West End offering, "'Twas the Night Before Christmas," and you add two sisters and another set of siblings into the equation. "It's really nice the way it's worked out," says "King Island" director Steve Perigard. "It's made it easier to create a family atmosphere onstage." "King Island" will also mark the return to the stage of both of Theatre IV's co-founders, Bruce Miller and Phil Whiteway. Both men say it was their children's involvement in the shows that prompted them to consider putting on the greasepaint again. Whiteway, who will share the stage with his son Alex, says, "It's a logistical thing after a while. You're ending up schlepping to several rehearsals a week anyway; you start thinking about volunteering yourself for the show." Miller adds, "It seemed like a nice family thing to do at Christmas time." Miller and his 10-year-old daughter, Hannah, will appear in "King Island" together. The third family unit consists of stage veteran Brenda Parker and her son Jimmy. Theatre IV joins more than a dozen other regional theaters throughout the country that are producing "King Island Christmas" as an alternative to standard holiday fare like "A Christmas Carol." The show tells the true story of a small village located on an island in the Bering Sea. When an Arctic storm traps a supply boat carrying the island's winter provisions, the villagers must band together to figure out how to reach the stranded boat. They decide to send out an oomiak - a canoelike vessel made with walrus skin. In an interesting anthropomorphic turn, Hannah Miller plays the oomiak. "Hannah heard the music when I was considering whether or not to do the show," says Miller. "She just fell in love with it." But Miller's position at Theatre IV did not guarantee his daughter a role. Director Perigard concurs. "Bruce and Phil are very firm about that: Their children have auditioned for me before and I haven't always cast them." Miller wasn't sure of a role himself, though his chances were pretty good. "I don't think anyone else auditioned for the part," he says with a laugh. While "King Island" may be new to theatergoers, Theatre IV's other holiday offering has been around for 15 years. "'Twas the Night Before Christmas" tells the tale of Clement Moore's inspiration for his famous poem, "A Visit from St. Nicholas." Maura Sinnenberg, sister to "King Island" cast member Caron Sinnenberg, plays a singing mouse in this show, as does Jennings Whiteway, another of Phil Whiteway's children. Theatre IV has always provided fun for the whole family with their Family Playhouse series. This year, part of the fun will be picking out who is related to whom onstage.