This dude literally has the same face as BB, are WB and the WG retarded.
The WG, heck yeah, but, honestly, I think Newgate knew.
Newgate raising his Captain's son without telling Teach he knew is totally something Whitebeard would do.
Whitebeard was protecting Teach from the WG, and got backstabbed in the worst way possible.
This also gives new meaning to Shanks and Newgate talking to each other: Shanks was like "Yeah, Rocks' son gave me this scar. He's a threat, Whitebeard."
Both Newgate and Shanks knew Teach was Rocks' kid in that conversation, IMO, looking back on it now.