Twoapenny,
Your description of what went on in your household while you were growing up made me feel really really sad --- especially the part where you felt that it was normal. I just want to support your perception that it was NOT NOT NOT normal.
Although obviously I am on this forum because I have had to deal with maternal narcissism, my dad was not narcissistic and, several years after his death, I am discovering that he actually exerted quite a lot of control over my mother. After his death, she became a lot worse ... until I took a cue from Dad's book and started confronting her when she acted badly. She seems to have gone back into the closet, for the time being at least. Anyway, my dad was a very strong man although he had some issues himself.
The reason I'm saying this is to say I think my dad maintained good boundaries with regards to sexuality. Some might even think he was prudish, but thank God he erred on the side of modesty instead of what you went through. It was the rule that (from about the age of 10 or 11) I wore a robe over my nightgown or slip when outside my room. He left the room once when a Hallmark special was showing a colt being born on TV ... even though he was a cattleman and had delivered calves and colts himself. He always had jeans with a belt hung near the bed, and put them on if he had to get up at night. I didn't have brothers or other young male relatives, so I wasn't real sure what male genitalia looked like until I was about 11 and I think saw a statue or something. He loved his grandchildren but NEVER even asked to touch my tummy while I was carrying them.
Some people might think he was prudish, but I tell you this to affirm to you that what you lived through was NOT RIGHT and it was NOT NORMAL. I have a healthy sex life with my husband and I think have a healthy attitude toward sex, and so my dad's attitude of modesty did not make me embarrassed or ashamed about sex. Instead, I think it kept me from a lot of confusion.
My dad had trouble with emotional boundaries --- he never quit trying to solve my problems and wrap me in cotton-wool --- but IMO that type of boundary issue is easier to deal with than sexual issues.
Again, I am so sorry that you had to live through that nightmare. I know that you have already stated you know now that what you lived through was abusive, but I just wanted to support your perceptions completely. Some people have said that sexual abuse is the worst, because you feel in your heart that what is happening is wrong, but the perpetrator says it's OK --- but then does everything possible to keep it secret. In your case the abuse was compounded by your mother who was in collusion with the perpetrator. In fact, I would call her a perpetrator herself.