Alec Baldwin has paid a touching tribute to his late father Alexander Baldwin on the 36th anniversary of his death.

The 'A Star Is Born' actor has opened up about losing a parent and how the passing of his dad - who died of lung cancer at the age of 55 in 1983 - ''effected [him] tremendously''.

Alec described his late father, who was a teacher, as ''uniquely caring'' and ''dedicated'' and admitted that he has looked to other men to be a ''mentor'' to him, but no one has been able to step in his ''irreplaceable'' shoes.

Alongside a picture of Alexander in a naval-style suit when he was younger and a portrait of him as an adult sat at a desk, The 61-year-old star wrote on Instagram: ''Today marks the anniversary of my father's passing: April 15, 1983.

My father was a uniquely caring, dedicated, stern, smart and, at times, funny man who served as a public school teacher and coach for 28 years until his death at age 55.

Beyond missing those who are no longer with us, beyond wondering where they have gone and how life might have been if they had lived longer, the loss of a parent sets in motion the ''orphan clock.'' The time when, after both parents are gone, one is an orphan in the world. With no one alive to parent you, which is a wondrous and vital calling.

My mother is still alive, but the death of my father effected me tremendously and set me on a course of seeking other men to advise me. To care for me. Mentor me.

No one has quite filled that position.

A mother, a father, under the best of circumstances, though never perfect ones, are irreplaceable.

I miss you, Dad. (sic)''

Alec - who has Ireland, 23, with Kim Basinger, and Carmen, five, Rafael, three, Leonardo, two, and Romeo, 10 months, with spouse Hilaria - opened up missing his father days after his wife tragically miscarried their fifth child.

The author admitted she is ''fortunate'' to be ''surrounded by such love'' and thanked everyone for the outpouring of support she has received since sharing her devastating story with the world on social media.

Alongside a picture with her children and the 'Rock of Ages' star, who she hailed ''pretty strong and amazing heartbeats'', Hilaria wrote on Instagram: ''There was no heartbeat today at my it's over...but I have some pretty strong and amazing heartbeats right here. I am surrounded by such love and I feel so fortunate.''

The yoga-lover added how important it is that people going through the same thing share their stories.

She continued: ''Thank you all for listening, for your support, and for sharing your own personal stories. We are stronger together...I hope this conversation continues to grow and that we stick together through both the beautiful and challenging moments in life. Much love and appreciation to all of you.''