What do you do when you have a 34 y/o stepson free loading and munching off of your wife and myself?

i have a 34 y/o stepson and his 2 girlfriends are living in our home.they paid no rent and party alot.one of his girlfriends is knocked up he is in to young girls.he lies and makes excuses for things that he does.he is very inmature for his age.he does work,but all his money goes to drugs and partying.my wife won't let him grow up and she goes along with everything he does.this is putting a buren on our marriage.my wife won't go to couseling.i have ask her serveral times to go.i am about to give up.i am disable and my wife does take good care of me.she is a good woman,but lets her son take advanage of her.