Wouldn't this be considered the norm though? Aren't most murders committed by family members and close friends? Murders by strangers are uncommon, given a child's lack of independence, wouldn't we expect them to murdered by their families more than anyone else?

As for men being more likely than women to kill and infant, well, I have no children, but I have very good male friends who have said in moments of frankness that they felt nothing for their children while they were infants and that it wasn't until they got older that they bonded with it. I believe that to be not uncommon.