My Nephew Eli Apple Is A 'Savage'

Michael Blackson says Eli Apple is ruthless with the Twitter fingers ... telling TMZ Sports he's not one bit surprised about his nephew's trash-talking antics -- 'cause it "runs in the family!!"

Apple made headlines throughout the playoffs for speaking his mind on social media ... going after opposing teams and gloating each time the Bengals came out victorious.

The actor-comedian told us he was cheering on his kin against the Kansas City Chiefs on championship Sunday ... but admits if he were Eli, he would have waited until after he won a Super Bowl ring to get at his contemporaries.

"I was rooting for him," Blackson said. "I always believe in talking smack once you get that ring. Once you…