ahhh congrats and welcome to the world of step parenting/Blended families..

It is def something that will try your relationship in all honesty but if you can get through it, it will make you so much stronger as a couple then you already are.

DF and I have been living together for a year now and it still has its testing moments... As Cate said the hardest part is no reacting defensively if he tells them off for something you may have let slide or he loses his cool (as long as its not a all the time thing)

You have to let him make mistakes, because he will make lots and you need to find a way to learn to address those mistakes between the two of you and also the kids because they cant feel that they can get away with anything but they also need to know that he or you can make mistakes and apologise.