Actor Tom Hopper and his wife Laura decided to speak about their son so that other parents "going through this ... don't feel alone," he tells PEOPLE
tom hopper and son freddie
Tom Hopper and son Freddie
| Credit: Courtesy Hopper Family

Although he frequently plays hard-bodied tough guys onscreen, at home, British actor Tom Hopper is all "soft inside" as a loving husband to wife Laura and father to daughter Truly Rose, 2, and son Freddie, 5.

Recently, the Game of Thrones alum and Laura, an actress and writer, decided to open up about their son Freddie, who is nonverbal, after receiving his autism diagnosis just before his fifth birthday in March. They've been sharing videos and photos on their social media accounts detailing their experiences, hoping to help other parents.

"We thought, we've got to do this for the parents that are going through this so they don't feel alone," Tom, 35, tells PEOPLE in the latest issue. "Because it can be a very lonely time."

He adds, "You have to trust each other and the journey. The right things will happen eventually, but it doesn't happen overnight. My son has autism, and he amazes me every day. His brain just works in a different way."

Tom and Laura first noticed their son was different at around 18 months. "The first thing we noticed was Freddie wouldn't turn around for his name," recalls Laura, 32. "From there, the older he got, the more of a gap there was between him and other children his age, in terms of his progress."

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tom hopper and family
The Hoppers (clockwise from left: Freddie, Tom, Laura and Truly)
| Credit: Laura Hopper Instagram

Adds The Umbrella Academy star, "He'd properly engage. We would be able to talk to him and he'd respond, but it stopped."

Laura says it was important for them to "recognize the regression." They both threw themselves into autism research and educational courses, but quickly realized, like all parents, that each child is unique, and no two kids with autism are the same.

"The biggest thing for us was learning Freddie," says Tom. "We've had to figure out what works for him and what doesn't."

One big win for the Hoppers was cutting out processed sugars from their son's diet, which they believe helped regulate his behavior. "We took Freddie off sugar, apart from certain fruits and honey," says Tom. "The difference was massive. It eliminated any aggression and is keeping [his moods] stable."

umbrella academy
Tom Hopper in The Umbrella Academy
| Credit: Netflix /Courtesy Everett Collection

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Tom says Freddie reminds him to take joy from simple pleasures like "laughing, running" and "playing in the garden," he says. And Truly, who is neurotypical, also keeps him and Laura on their toes.

"She’s a Daddy's girl," says Laura. "Sassy little thing. She's going to walk all over Tom when she gets older."

"She's a Daddy's girl and I adore it," says Tom. "She's going to walk all over my wallet."

Watch Tom in the new season of The Umbrella Academy, now streaming on Netflix.

For much more on Tom Hopper and his family, pick up the latest issue of PEOPLE, on newsstands Friday.