'Me and uncle Will!' Justin Bieber shares a photo of himself with his arm around friend and mentor Will Smith

'Me and uncle Will:' Justin Bieber shared a picture of himself and actor Will Smith via Instagram on Wednesday

Some friends are practically family.

And Justin Bieber clearly feels that way about Men in Black actor Will Smith; sharing an Instagram picture of the pair together entitled 'Me and uncle Will'.

The photograph shows Will, 44, draping his arm over his young friend's shoulder and flashing a peace sign at the camera.

Wearing a blue baseball cap and white T-shirt, Justin leans into his buddy and poses for the snap.

With his heavily tattooed arm and chunky gold jewellery on display, Bieber looks markedly different to the famously clean-cut Smith.

In red shorts and a black vest top, the industry veteran's only hint of bling was a large diamond stud in each ear. 

The high-powered pair are old friends, with Bieber previously stating that he is 'part of Will Smith's family,' and Smith echoing the sentiment by labeling the Somebody To Love singer 'fantastic.'

Smith has also stuck up for the 19-year-old in the past, defending him against those who believed Bieber to be going off the rails.

Bieber caused a stir with a spate of erratic behaviour earlier this year, which saw him get in trouble with police for speeding and allegedly spitting on a neighbour.

He also disappointed fans by turning up very late for a concert he gave in the UK.

And observers began to draw parallels between the pop sensation and tragic singer Michael Jackson, after Bieber's pet monkey Mally was seized by customs in Germany when he failed to produce a health certificate for the animal.

Speaking on Capital FM in April, the Fresh Prince of Bel Air star defended Bieber's behaviour, passing them off as youthful high-jinx.

'There are things that are just simple and normal for a 19 year-old to do.  When I was 19 there was no Twitter, the things that I was doing – I was able to have privacy because everybody's phone didn't have a camera on it,' he explained.

Bieber tweeted Smith's comments, saying: 'Will Smith is the man!' Before adding a note to close friend Jaden Smith: 'u r cool too :)'