Sean Berdy, Vanessa Marano Sean Berdy, Vanessa Marano

Switched at Birth's Bay (Vanessa Marano) and Daphne (Katie Leclerc) have a lot on their plate. After learning they were swapped as newborns and that Daphne's mom, Regina (Constance Marie), has known for quite some time, Bay's MIA biological father (guest star Gilles Marini) returns in Monday's finale.

Exclusive: Gilles Marini joins Switched at Birth as Bay's biological father

"We're not sure if he's a good, well-meaning guy," Marano says. "He's coming into this thinking he didn't have a daughter because, where we left off with him, he thought [Regina] had an affair with someone else and Daphne was a lovechild."

Exclusive: Gilles Marini joins Switched at Birth as Bay's biological father

In the interview below, Marano and Leclerc also talk about Bay's new romance with Daphne's best friend, Emmett (Sean Berdy). While Marano calls the pair "kindred spirits," Leclerc reminds us that Daphne gave up her relationship with Liam for Bay, yet Bay continues to date Emmett. Will the girls force Emmett to choose between them in the finale? Plus: Leclerc shares the reaction she's received from the deaf community.

Switched at Birth airs Monday at 9/8c on ABC Family.