The R&B crooner wrote a tune specifically dedicated to Kobe -- and by extension, to the basketball star's daughter, Gianna -- called "Can't Say Goodbye." We got a video of Brian playing it on guitar, and it's incredibly touching and sweet. Check it out for yourself ... but again, waterworks.

In the video, Brian says he wrote the song ... but can't really take credit, because it wrote itself. The lyrics touch on saying other versions of "goodbye" without actually uttering the words themselves because it's just too hard and so final. Frankly, it's beautiful.

We're told, Brian put this together in the hopes that it will help people begin to heal from the loss.

Of course, Brian and Kobe had a relationship. The NBA superstar was once featured on one of Brian's songs back in 1997 called "Hold Me." KB had a rap verse on it toward the end.

He's also a huge Lakers fan in general and included a ton of footage of Kobe in a tribute video he put together to honor the City of Angels. That track's called "I Love LA."

With all that said, it's no wonder the death of Kobe has affected Brian the way it clearly has. No word if this song will make its way onto an album of some sort, but we expect it'll reach the masses eventually.