ABC Family’s “Shadowhunters” saga series is filling out. Alberto Rosende and Emeraude Toubia have been cast as Simon and Isabelle, Variety has learned.

The two actors join Dominic Sherwood, who will play Jace, whose leading lady, Clary Fray, is yet to be cast.

Simon, intelligent and very handsome in a non-calculated kind of way, is Clary’s longtime best friend. An accounting student by day, Simon spends his free time performing in a band. His loyalty and feelings for Clary are tested as he fights alongside her on an epic journey.

Isabelle is an exotic-looking, beautiful Shadowhunter. An expert with her whip, and a trained fighter who can kill it in high heels, she’s just as lethal as she is attractive. Her one weakness, however, is her choice in men, as she always goes for the bad boy.

Based on the bestselling “Mortal Instruments” books by Cassandra Clare, the supernatural series follows 18-year-old Clary, who finds out on her birthday that she is not who she thinks she is, and that she actually comes from a long line of Shadowhunters — human-angel hybrids who hunt down demons. When Clary’s mother, Jocelyn, is kidnapped, she is thrown into the world of demon hunting with mysterious Shadowhunter Jace (Sherwood) and her best friend, Simon (Rosende). Living among faeries, warlocks, vampires and werewolves, Clary begins a journey of self-discovery as she learns more about her past and what her future may hold.

The project marks the cabler’s first-ever “saga-to-series,” hoping to find a loyal audience in ABC Family viewers who already tune into the network for franchises “Twilight,” “Harry Potter” and “The Hunger Games.”

“Shadowhunters” is produced by Constantin Film and exec produced by Ed Decter and McG, who will direct the first episode. No premiere date has been set, but the series goes into production this month.