WTF Moment - Another Houseguest

Yesterday I received a phone call from my manager about a mandatory meeting.  (Amazing how mandatory things for both my jobs always occur when I'm not supposed to be at work.)  When I returned home from the meeting my wife informed me that her niece was coming to spend the night.  WTF?  You didn't ask if it was okay with me?  We don't live in a mansion or a hotel.  We stay in a 3 bedroom house.  The nephew and his girlfriend sleep in one room.  My two oldest sleep in a room and my wife sleeps in the main bedroom with  the youngest.  I sleep on the couch. I'm guessing the niece slept in the room with the nephew since they are brother and sister but I imagine that was awkward as fuck.  Maybe not since the niece is a lesbian.  Regardless, I just don't understand why my home has become a parking garage and a hotel for her family every time they are in the area.