Friendship is a big theme in Henry Winkler’s life, and his latest kids’ book. “In Alien Superstar, there are thoughts on what it takes to be a really good friend,” Henry, who grew up feeling like an outsider due to his dyslexia, tells Closer. “I spent my youth thinking I was less-than.”

Of course, the Happy Days star grew up to become a beloved, well-respected actor — but he never lost his empathy or desire to be a true friend. Henry, 75, and his family have been close with actress Marlee Matlin since she was a child with big dreams despite her deafness.

“At 12, she danced to music she couldn’t hear,” marvels Henry. Many felt Marlee’s disability would be insurmountable in an acting career, but Henry and Stacey, his wife of 43 years, encouraged her in good times and bad. “She’s like a second daughter,” he says.

Henry Winkler Talks Longtime Friendship With Marlee Matlin: 'She's Like a Second Daughter'

At 21, Marlee won an Oscar for Children of a Lesser God but also attended drug rehab and escaped a turbulent relationship with her much older costar William Hurt. “It’s Oscar night. My doorbell rings, and Marlee’s got the Oscar in her hand,” Henry recalls. “She says, ‘Can I stay with you for just the weekend?’”

Marlee ended up living with the Winkler family for two years. “They always gave me words of support and advice,” says the actress. “You couldn’t find a more genuine family.”

When Henry began writing children’s books in the early 2000s, he drew on his compassion as much as his imagination. Alien Superstar: Hollywood vs. the Galaxy is the final volume in a best-selling trilogy for middle graders.

Henry Winkler Talks Longtime Friendship With Marlee Matlin: 'She's Like a Second Daughter'
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“It’s not self-help. We are the book you put in your backpack when you want to laugh and escape,” Henry says, explaining that lessons about acceptance and inclusion “sneak up” on his readers.

But it’s been extremely gratifying when his stories hit their mark. “When parents tell me of their child identifying with our characters. … Well, if I had to say what I was proudest of outside my family, I’d say it’s the books.”