Hello, I found this on the internet for your brother.
Smoking is very inhealthy regardless whether he has Crohn's or not, but I am sure it's hard for him to stop especially, if he's been a smoker for years.
He's lucky to have someone who is concerned for his well being. Is he being treated for his Crohn's? I've had Crohn's since 2010 and am on Imuran and Remicade Infusions.
Good luck to you and him!