Robin Williams' son Zak has paid a touching tribute to his late father on what would have been his 70th birthday

Alongside a black and white snap of the 'Jumanji' actor - who was also survived by Zelda, 31, and Cody, 29, whom he had with second wife Marsha

- Zak wrote on Instagram: "Dad, on what would be your 70th birthday, I would want you to know that your incredible spirit lives within us.

"Our family will be celebrating you and your memory today. We miss you and love you always!"

Robin tragically took his own life after being diagnosed with Lewy Body Dementia in 2014, aged 63, and Zak has been open about his own struggles with mental health and how he turned to alcohol to self-medicate after being diagnosed with PTSD (Post Traumatic Stress Disorder) following his father's passing.

Speaking on 'The Genius Life' podcast, he said: "I was heavily drinking to manage my mental health where it created very harmful issues. For me personally, I was having health issues.

"I was experiencing some psychosis and when I spoke with a psychiatrist I was diagnosed with Post Traumatic Stress Disorder."

The 38-year-old actor - whose mother is Robin's first wife, Valerie Velardi - also suffered from disassociation, which includes symptoms such as not feeling connected to your own body, and sought help immediately and continues to benefit from mental health services and therapies.

He said: "I found myself hitting rock bottom when I wanted to just be numb. I found myself wanting to drink alcohol and just not think. That was something that was really dysregulating for me.

"I found myself waking up in the morning and feeling like I was having a dissociative experience, but I just didn't want to be living the life I was living. I realised something had to give."

He added: "I can't stress how important service is to my life.

"The other thing is I found community support groups to be really helpful. I'm in a 12-Step program, that's very helpful for me personally. For others, it might be connecting through community organisation or through sports, there's any number of things."