Chandler Jones would BEAT THE HELL out of his famous UFC brother, Jon Jones ... so says the Arizona Cardinals DE himself, who tells TMZ Sports, "I'll beat Jon Bones' ass!!"
"Listen, he has the longest arms in the UFC," Chandler says ... "My arms are longer than his. That's my brother, I love him to death, but I'll kick his ass!"
The clip is hilarious ... but Chandler seems dead serious -- telling us his older brother would take the first real L of his career if the two really did square up.