The Protective Instinct is not owned by mothers alone.
Any grandparent knows how protective they are of their grandchild.
Let's not forget Dads, known for, or considered responsible for, the protection of their children. Both parents, both sexes, are expected to be protective of their grandchildren.
You may also find that teachers can be very protective of their students. I'm sure many others that work with kids, mentoring them and helping them grow, and multiple extended family members find are, can be, or find themselves in a protective role.
I have heard so many old myths about stepparents- That they are unable or incapable of parenting. They do not have the natural instinct that a biological parent has. Many parents in a custody battle (or to their friends...) would definitely, easily, and immediately argue that a stepparent lacks all parenting skills and does not care about their child.
Wrong. I believe that stepparents are like parents and have a great deal of protective instinct for their stepchildren. My guess is that an equal amount of stepparents hold that capability as biological parents- as of course, not all biological parents are "good" parents with all those innate instincts.
Stepparents invest their lives, future, money, home, skills, and possibly all of their parenting ability (if they do not have their own kids) into their stepkids. Some may not be fantastic, just like regular, everyday parents, but many are just like me. We have invested a ton into these kids, and when their parents aren't there- We do fly into action to protect them.
Actually, a great point of contention between stepmoms and moms is this exact feeling of protection coming from the stepmom. Many, many stepmoms feel wholly protective of their stepkids, and feel that the mom is not. Whether this is true or not, as it is possibly just different perspectives (...), it is still the case that most stepmoms feel that they do know their stepchild and are quite protective of them given the amount of time they spend with them and on them. I know for a fact that I have felt it repeatedly over the years and want to step in and protect them, do something, change their situation, and be a parent. I absolutely have a natural, caring, parenting instinct to care for them, protect them, and take action on their behalf. My husband can also vouch for this, as I am often more likely to want to fly to their aid in situations that are not specifically about physical safety.
So often moms argue that their child is not safe with the stepmom. The evil, evil, unsafe stepmom.
We are bewildered, confused, shocked- because we feel the opposite of what is described. We know what we've invested and that we do have (some sort of) relationship with the children, despite its imperfections and lack of shared blood.
Just as a teacher, coach, mentor, pastor- a stepparent, who is with the child more than the aforementioned roles, feels protective of "their" stepchildren.
Further, a stepmom who seems to be less than involved has likely been driven to that or asked to be that way.