Hermione considered the whole of what she knew about Walburga Black, and Sirius’ childhood.  It wasn’t much, but all of it was bad.   She wouldn’t have put it past that woman to have a room to lock her children in.  She was surprised, given his own miserable experiences with the Dursley’s, Harry had left it.  He must have seen that in her eyes because he said, a little defensively, "There’s a lot to do at that place, and Kreacher tries, but he’s old, and I hate cleaning up, and you know Ron."