Looking back at his father's struggle, Zak admitted that he felt a sense of "helplessness" as he watched his father's emotional, internal struggle.
"I didn't know what I could do, or how I could be of the best support," Zak explained. "We all loved him so and found it difficult because he wasn't always open to sharing his personal pain and struggle… And we noticed that over a period of time."
Robin Williams' eldest son Zak reflects on his father's struggles, as the fifth anniversary of the actor's death approaches 💔 pic.twitter.com/krlYkTAh3r
The actor's son also admitted that the most "heartbreaking" thing for him to see was watching his dad still go out, perform stand-up, act in projects and make others laugh while he was personally in such a dark place.
"He still went out and wanted to share his feelings of laughter and humor with the world… While he was suffering and struggling, he still went out and performed," Zak reflected. "I admire him and loved him so, and having to share him [with the world] was hard."
Recently, Zak and his fiancee, Olivia June, welcomed their first child together on May 22, and he proudly paid tribute to his late father by naming his son McLaurin Clement Williams -- McLaurin being Robin's middle name.
Zak is Robin's son from his marriage to first wife Valerie Velardi. Robin was also father to daughter Zelda and son Cody from his second marriage, to Marsha Garces. He married his third wife, graphic designer Susan Schneider, in October 2011.
If you or someone you know needs help, please call the National Suicide Prevention Lifeline at 1-800-273-TALK (8255).