Isn't it interesting, the different ways in which we all see Sheila. I wonder who she was really.
I don't believe she was looking forward to a happy life with the family. Not the English one, anyway. I think, when her biological mother left she took with her all Sheila's hopes of what might have been and she may have been left with what was. Certainly, she seems to have accepted religion but I suspect more to please June than herself. I get the feeling that she may have had to work very hard at pleasing June and may even have tried to persuade the boys to do the same.
I can't go along with Jeremy having a mental illness. I'll settle for personality disorder, though.
Good post.
Personally I think that Sheila, if responsible for the killings, did them to "please" June - in a skewed, insane logic.
I think that might be the reason Sheila committed suicide in the room where June was lying dead. "Look mum, I ridded the world of all the evil, I am a good girl, now love me." - Yeah, I made that up, just a train of thoughts, I know I will be roasted over a slow fire!

Devil´s children and all that. That started with June. She called Sheila the Devil´s child, who in turn called her sons the same - she just went further; they were "women haters, especially Nicholas", they were capable of raping and killing her.
Why the poor boys weren´t taken from her right there and then is a mystery to me.
In the doctors´ statements (especially Dr. Furgusson) you can read between the lines that a lot of "hand washing" was going on.