Here’s my worshipping 10th child theory.
As said before, The 10th child was the one that crossed out the names. But I think that it also lives in mother’s room but never leaves it, (unless to cross something out at nighttime) not ever since it realised that only mother can see it. Why’s that? First of all, Mother was an alcoholic —mostly wine— and even when she turned pregnant, she kept drinking. Because she didn’t realize that she was having a baby… until it was too late. After her embryo disintegrated, she has more toils than she has toilet paper. And she put on vhs tapes to cope with it, HOWEVER she started hallucinating what looked like an awfully tall 9 year old, it was difficult to see any color in the kid except the VHS cubes. It must’ve said something like “I forgive you.” and then ”And forgivers have to help the other, turn the situation around.” That HAS to be why it’s called the backwards house. And the backwards house was actually a normal cartoon that Mother made and made it a custom VHS tape. She had chills even thinking about inserting the tape in. But when she did, the spirit inserted every soul into the right vessel the milisecond before the film started and before it’d finally be the tenth child. This still helps mother too, she wouldn’t have turn to alcohol or betray her children ever again.