At first I assumed it to be just an unaffiliated parody account. However Jang has shown he can take himself not seriously, such as in HALL OF JANGS video, and the voiceovers of recent Gnaj videos have a very similar sounding voice to Jang's except pitched higher, so I'm starting to believe that if Gnaj isn't Jang himself, he has help from Jang. 

What are your thoughts?

I'm not really sure, been thinking about it for a while, but it's not my place to make accusations. 

It is Jang himself of course 

Something else of note is that even though Jang denies being Gnaj in the Beyond the Brick interview, he holds Gnaj in high enough regard to list the channel on his "Feature channels" list on his page (the only other non-Jang channels listed are Beyond the Brick, Sariel's Bricks and Pets, and just2good, all very popular channels)

I think Gnajbricks is Jang