It's not about the age range - it's about the step-parent being a parent to a child and then deciding to have a sexual relationship with that person.
Of course there's circumstances where a step-parent was never actually in a position where they were parenting their partner's children and it wouldn't be as abusive to pursue them after a break up. But that's the exception to the rule.
The post doesn't specify a gender for the victims.
But so glad that you felt the need to chime in that it's not all men.