Group of friends on a night out discussing upcoming wedding of friend (we'll call him Bob) to his long term gf. Bob is unsure and group agrees that Bob is a different with gf around... minding what is said, has to give lots of attention to gf. After many more drinks there's questions like "who would you rather sleep with, Bobs gf or married friends wife?" Single friend says neither 'cause they're taken, married friend says obviously my wife, Bob refuses to answer and changes subject. Should I tell my friend that he needs to be sure before he marries her, or ignore lads banter and let him get on with it?