My 20yr old stepson plays wow all night at wkends and sleeps all day..?

his father wont tell him to get off it and sees no harm..but he has been on it 8yrs and showin no signs of goin of it..he is missin days from college or goin in late and says he could have a girlfriend if he wanted but has no time.i tried tellin him no noise and off after 12 but ignored most time...really need ideas wat to do me and his father end up arguing over it and stepson knows his father not back me up as he doesnt c it as problem..my marriage of a year is rocky as a result.my own daughter is up at 7am and away to college 14miles away and not home till 6 or 7 in evening and works part-time in summer and feels resentful that her stepbrother is given a lift to college by his dad,his college 3miles away..