Will Smith has joked he is "still trying to figure out what he's doing" when it comes to being a father.

Jaden Smith and Will Smith

Jaden Smith and Will Smith

The 'Focus' star made the comment as he posted a sweet message to his son Jaden on his 18th birthday.

He wrote on Facebook: "Happy Bday, Jaden! You're 18 years old today. And I'm still tryna figure out what the hell I'm doing. : -) (sic)"

And Jada Pinkett Smith, who also has 15-year-old daughter Willow with Will, also wrote a tribute to "one of the brightest lights of her life".

Writing on her social media accounts, she added: "Jaden, You are the prince of my heart. I have no doubt that you were born to me to show me how deeply I can love. You are one of the brightest lights of my life. You are my son, my friend, a walking embodiment of my soul, my treasure. Happy Birthday Mr.18:)))) Ma (sic)"

Meanwhile, the 47-year-old actor previously described his son as "100 per cent fearless".

He said: "There's a really powerful internal quality as an artist that as parents we encourage. You gotta get out on the edge, you have to try things, you have to be comfortable doing things that people don't agree with, and you have to be comfortable doing things that you could fail.

"And Jaden is 100 per cent fearless, he will do anything. So as a parent it's scary, it's really terrifying - but he is completely willing to live and die by his own artistic decisions and he just doesn't concern himself with what people think."

It is something Jaden himself echoes, insisting he doesn't worry what other people think about him.

He added recently: "You just have to believe in yourself, you know. The world is going to keep bashing me for whatever I do, and I'm going to keep not caring. I'm going to keep doing the same things - I'm going to keep doing more things."