WB Beefs Up Its Prime-Time Lineup : Television: With the addition of Sunday, the network will have two nights and 13 hours of programming, aimed at kids, teens and families.

The WB Network will inaugurate its second season with a Sunday night block of comedies and a slate of new series featuring such stars as Kirk Cameron and former “Saturday Night Live” performer Ellen Cleghorne.

Warner Bros., which launched the network last January with a lackluster performance in its Wednesday night block, also put a surprise twist in its announcement Monday in making “Sister, Sister,” a comedy about identical teen-age twin girls that was canceled by ABC last week, a cornerstone of the WB lineup.

“Sister, Sister,” which stars Tia and Tamera Mowry, will lead off Wednesdays nights at 8, and also will air Sundays at 7:30 p.m. Ironically, the comedy is produced by Paramount Studios, the parent of the United-Paramount Network, Warner Bros.’ rival in the upstart network race.

With the addition of Sunday night on Sept. 10, the network will have two nights and 13 hours of prime-time programming each week. An hour of children’s shows will also premiere Sept. 9, with a three-hour block on Saturday mornings. The WB shows will be aired locally, as last season, on KTLA-TV Channel 5. In addition to “Sister, Sister,” new shows for the network include an animated series, “Steven Spielberg Presents Pinky & the Brain,” a spinoff of Spielberg’s “Animaniacs,” which will kick off the Sunday lineup at 7 p.m.

A comedy featuring Cameron, formerly of “Growing Pains,” will air at 8 p.m. Sunday. The show, tentatively called “Life Happens,” stars Cameron as a bachelor and recent college graduate who unexpectedly becomes a parent to his three siblings.

“Simon,” which the network described as “a Forrest Gump-like tale of a youthful wide-eyed optimist in New York,” will follow at 8:30. The series stars comic Harland Williams and is from Danny Jacobson, the co-creator and executive producer of “Mad About You.”

At 9 p.m., Jackie Guerra will star in “Girlfriends,” which was described as a Latino “Living Single.” The comedy will be followed at 9:30 p.m. by “Cleghorne,” starring Cleghorne in a comedy about a single mother working in a public relations agency. Garrett Morris, another “Saturday Night Live” alumni, also stars.

On Wednesdays, “The Parent Hood,” with Robert Townsend, will return for a second season at 8:30 p.m., followed at 9 by a revamped version of “The Wayan Bros.” that will feature additional cast members and “less coarse language” than last season, officials said.

“Unhappily Ever After” will return at 9:30 p.m. “Muscle” is the network’s only offering from the first season that will not return.