Don't get me wrong. I like J.K. Simmons and I have enjoyed Jenna Elfman since Dharma and Greg, but there's a big-ass elephant on the set of NBC's Growing Up Fisher which a better casting director could have avoided and guarantees the divorced parents can never reconcile.
By itself, this wouldn't be bad. There are plenty of May/December romances and an older actor with a younger actress is a showbiz staple, they're both adults and they can do what they want, but a big part of Elfman's storyline is that she got pregnant as a teen. I'm pretty sure they have even joked that the couple hooked-up on their second date and she was pregnant at her prom.
One of the child characters, Runyen, dismissed his friend's father as being "about fifty" and Simmons could be playing younger than his actual age, but few would think that Elfman is playing older than forty-two. This means that if the other clues about their courtship are taken into consideration, best-case, Simmons is playing someone who impregnated a high school senior when he was twenty-five and worst-case, using their actual ages, he was thirty-four.
Compounding the issue or proving the point, Simmons' previous show was Family Tools, in which he played Leah Remini's father. IMDB lists Remini as 43.
Everything else about the show is solid. It's not the most exciting show on television and there are probably few who would consider it appointment viewing, but in the tradition of The Wonder Years, it's a fine effort. This includes the performers, as long as the parents don't reconcile and the writers back away from the big red flag marking their cast.