If he's a "hard follower" of Joe Rogan than he likely won't be interested in other content. Rogan is a fool, but that's why people find him appealing. Content that is insightful and educational is the opposite of the junk food of Rogan.
Maybe instead, when Rogan says something like "Bro did you know like the pineal gland of the chimpanzee produces anti-covid hormones? This is just what I've heard. Look it up. By the way did you see the tree growing in my toilet?" You can help your sibling by teaching them ways to think, reason, and critically evaluate the BS that freely flows from the Roganverse.