Mom and her bf kill her 6 yo son and dump his body in Ohio River

What normally happens when a mother gets a bf bcz it’s like 4/5 of murders of children involve a mother and her boyfriend. I remember one mom and her bf set the child on fire. Is it a way of getting back at the baby daddy, releasing the anger for being left to raise a child alone ama coz there seems to be a correlation between a mother having a boyfriend and abuse, neglect and even murder of her child. So sad. RIP to the young man.