As previously reported, the 20th Century Fox TV and NBC comedy, which was recently given the green light, is co-written by "Glee"'s Ryan Murphy and Allison Adler. Murphy will also direct.
The single-camera project is described as "a heartwarming comedy about a blended family of a gay couple, Bryan (Rannells) and David (Bartha), and the woman who becomes a surrogate (King) to help them start a family." Barkin is cast as the surrogate's glamorous grandmother.
Rannells' previous Broadway outings include leading roles in Jersey Boys and Hairspray.
Barkin, who made her Broadway debut last season in Larry Kramer's The Normal Heart, took home the Tony Award for Featured Actress in a Play. Bartha, who is known for his performance in "The Hangover" films, has been seen on Broadway in Lend Me a Tenor.