Who controls the lease or whatever? Are you living in their house or is a mutual kinda deal?
If former then I say get out and get out as soon as is reasonably possible.
If the latter than I say knock the whole fence down and if the roommate gets pissy about it tell him he'd be better served by keeping a better eye on his kid than locking out your wife from her own home.
Lazy-ass parents FTL //content.invisioncic.com/y282845/emoticons/mad.gif.c18f003ab0ef8a0d9c27ca78d77a6392.gif
If it is your house then tell him, his wife, and his kid they need to find somewhere else to be and pronto.