Actresses Elizabeth Pena and Stephanie Beatriz will guest star on ABC's "Modern Family" as Sofia Vergara's character's family, the executive producer said. Pena, who was in "La Bamba" and "Rush Hour," will play Gloria's [Vergara] mother while Beatriz, who has appeared on TNT's "The Closer," will play her sister, Entertainment Weekly reported Friday. "There's a bit of a competitive relationship between Gloria and her sister that will be fun," executive producer Christopher Lloyd told EW. "The mother is the formidable, domineering character in the family, and has a complicated relationship with Jay [Ed O'Neill]. I'm not sure she's ever completely accepted Jay, and they lock horns in the episode." The 12th episode, "Fulgencio," begins shooting Monday.