I presume that, in the archaic environment, when a man mated with a new woman she would have encouraged him to kill offspring from a previous coupling. This explains the “wicked stepmother” myth. Yet today we insist, quite blithely, that we’re all “cool” with our stepparents.
I think men would be indifferent otherwise, and there are evolutionary reasons for them to be so from an investment perspective. It’s a case of the Lady Macbeths. Women exert immense covert psychic influence to inspire violence, aggression, and competition in men.