Maybe I have a complicated relationship with my siblings but all the people that are talking about how someone had to have known what was going on in that guys house is so weird to me. I've lived in my condo for 7 years, my mother hasn't been over in 3 years, my dad since I bought it, and between my 2 siblings and 2 half-siblings only my sister has been over. I've never been over to my brother's apartments, never been upstairs in my half-brother's house and never been into the bedroom areas of my half-sisters house.
And it's not like I am a hoarder or living in filth or anything, it's not there has never really been a reason for them to come over to my house, if they are in the neighborhood I'll normally just meet them downstairs or at a bar or restaurant or something. As for off limit areas if I'm having people over my bedroom is generally off limits if not at least my giant walk-in-closet big enough to hold a sex-slave, not for any creepy or seedy reasons, it's just normally have bills or laundry or whatever shoved in there.