I think, now that we know it's a step-son, the best bet is like some above have said.
Play the long con. All of a sudden become agreeable. Let him study. Encourage it. Tell the brother, "Thank you so much!"
Perhaps your wife's watchful eye will eventually grow drowsy and you'll be able to unWitness to your step-son when opportune moments present themselves.
That, coupled with him going to college, will in all likelihood wake him up.