His girlfriend, Nessa, is a top DJ at Hot 97 in New York (and she's also friendly with Chris Brown).
The other question ... what's Kaep doing in NYC?
Unclear how Broner got facetime with Colin -- it's possible he just asked for a quick selfie.
As for the concert, we're told it was lit ... a bunch of stars were there including Fabolous, ASAP Ferg, Young Ma, Lil Kim, Cam'ron and more.
Kaep and Chris Brown have been friends for a while -- the singer was a big supporter of Colin's national anthem protest and his 'Know Your Rights Camp' campaign. They posed for a pic together back in January.
Colin Kaepernick turned up in Brooklyn, NY on Monday -- hanging at the Chris Brown concert at the Barclays Center where he posed for a photo with boxing star Adrien Broner.
TMZ Sports has obtained the suicide note Aaron Hernandez wrote to his fiancee, Shayanna Jenkins-Hernandez -- in which he tells her she will be RICH after he kills himself. It's not hard to…
So many questions ...
The other theory is Colin is perhaps talking to an East Coast team looking for some QB help -- aka the Jets.