BURBANK, Calif. — Grandma is mad. Her grown daughter, Bex, who got pregnant as a teenager, just blazed back into town and let a big secret slip. Grandma had raised 13-year-old Andi to believe that Bex was her older sister. Well, the truth is a tad more complicated.

Meanwhile, Andi’s school life is only a little less unsettling. A boy is coming to terms with his sexuality. And Andi has her own budding love life to consider.

The latest from MTV?

Hang on to your mouse ears: Disney Channel — land of safe, sweet sitcoms — is exploring this charged terrain with “Andi Mack,” a comedic drama aimed at children 6 to 14 and their parents.

While it is just one show, it represents a startling new direction for the squeaky-clean network, whose ratings are decaying as children, reaching puberty earlier and raised on the oh-so-cool Netflix, gravitate to live-action programming with more edge and authenticity.