Watch Brothers and Sisters Season 4 Episode 15 Online Free Streaming Video: "A Valued Family" - The Walker family shares love and loss on Valentine's Day as Sarah rediscovers the love of her life (guest starring Gilles Marini as Luc Laurent), Kitty makes a grand but heartfelt entree in to politics with her family and new campaign manager by her side (guest starring Cheryl Hines as Buffy).