I had not read previously that marriages with steps are 50% more likely to break apart. Certainly a believeable figure.

What you say about giving power is true to a degree but steps can create such turmoil it just isn't worth it. There comes a point where unless you're going to literally lock them in a room for the duration.

The hardest to endure and therefore the hardest to fight is the non-custodial fathers fear of his kid(s) wanting to stop visiting.

Next is when they are in the faces of a female step as being the nesting member of our species they take it as personal failure.

It takes a strong willed bio-father to do stay the course and I completely understand the step-mother that can't take the tourmoil anymore.

Frankly I wish there could be a law against step-parenting. You are free to divorce but no marriage or shacking up until all kids are 18+ in the proposed union and having a bio-kid(s) changes nothing. The new kid simply stays with mommy until the others are 18. Of course that's not feasible for now - western governments don't have that sort of power yet.