Nicolas Cage -- The Dysfunctional Family Photo

Looks like hell officially froze over ... Nicolas Cage, his baby mama and their alleged wife-beating son all hung out together for FUN on Monday night ... which NEVER happens.

Weston Cage had a gig with his metal band at Whiskey a-Go-Go in Hollywood ... when surprisingly his mom -- Christina Fulton -- and famous dad showed up to cheer him on ... even though the family is as functional as the Greek economy.

But this time was different ... the happy fam snapped a pic (above) ... and we're told no one got hurt.

So, we recapped some of their past hobnobs ... just to see how far they've come.

-- Nic Cage and baby-mama Fulton hit up a courthouse to settle a nasty $13-mil lawsuit
-- Nic tells TMZ "I hope Ms. Fulton will come to her senses one day and get some help."
-- Nic sends an employee to hunt down Weston ... who then beats the crap out of him.
-- Weston is taken for a "mental evaluation," but his mom is banned from the hospital.
-- Fulton tries to get conservatorship of Weston ... against his wishes.
-- Weston tells TMZ "I want no contact with Christina Fulton and will never undergo the torment she put me through ever again."