Actually, I think it's the mother's boyfriend, followed by the mother.
Both are her fault, of course, but in the former case she's not technically guilty.
A 1999 US Department of Justice Study concluded that between 1976 and 1997 in the United States, mothers were responsible for a higher share of children killed during infancy while fathers were more likely to have been responsible for the murders of children age 8 or older.
So under 8, watch out for mom. The propaganda is all aimed at excusing nutty women, and blaming men for all the evil they can find,,, so it’s excusable that you believe that. Many people do.