THE WALKER FAMILY CONTINUES TO GROW, ON ABC'S "BROTHERS & SISTERS"

"Father Unknown" - Parenthood is questionable for more than one member of the Walker family, as Justin keeps a closely guarded secret about the true paternal identity of one of his siblings and Scotty makes a shocking discovery that will bring a new life into the Walker family fold, on "Brothers & Sisters," SUNDAY, APRIL 24 (10:01-11:00 p.m., ET), on the ABC Television Network.

"Brothers & Sisters" stars Dave Annable as Justin Walker, Sally Field as Nora Holden, Calista Flockhart as Kitty Walker, Rachel Griffiths as Sarah Walker, Luke Macfarlane as Scotty Wandell, Gilles Marini as Luc Laurent, Matthew Rhys as Kevin Walker, Ron Rifkin as Saul Holden and Patricia Wettig as Holly Harper.

Guest starring are Isabella Rae Thomas as Olivia, Roxy Olin as Michelle McGregor and Deirdre Lovejoy as Marissa Crandall.

"Father Unknown" was written by Molly Newman and Gina Lucita Monreal and directed by Matthew Rhys.

"Brothers & Sisters" is broadcast in 720 Progressive (720P), ABC's selected HDTV format, with 5.1-channel surround sound. A TV parental guideline will be posted closer to airdate.

This episode will be available on ABC.com the day after airing on the network for users to watch online.