Justin Bieber -- I Put a Roof Over My Family's Head ... In Canada

Justin Bieber's dad is living in a pretty badass Canadian home ... along with his two kids ... but TMZ has learned, JB is the one who sprung for the place.

Sources connected to the Bieber family tell us ... Justin wants to make sure his half-brother and half-sister are living in a really nice home, so he shelled out a cool $850k in cash for a 5-bedroom cabin-style pad in Ontario, where they live with their dad.

We're told ... this isn't a case of the family sponging off of Justin -- it's Justin who made the offer to the family.

The house is located way out in the Canadian wilderness in a small town of roughly 8,000 people.

But it's not like the family is trying to get off the grid -- the family name is plastered right on the mailbox.