As a step-parent of about 6 years now, I am all too familiar with your predicament. My position is that I am a dad. My girlfriend's children may not be mine biologically, but I will parent them as if they were. I can't help it. In our household we had to deal with the issue of who dad was, but differently. The youngest had picked up the idea that the biological father was available as a weapon she could use against me. This really baffled me because I had never attempted to replace him, have never stood in the way of them interacting, and when talking about it with the kids, have never referred to myself as their father.

In your case, it seems to me that the real problem is not the fact that you have lovingly embraced a child that is not biologically your's, nor is it the reasonable response of a child that has been quite receptive to your affections as a parent. Someone is feeling quite threatened by the natural developement of your relationship with this child. And for that person I feel quite sorry because that is not your problem. You are the woman of the house, and that means that everyone in the household falls under your umbrella of nuturing. If you could, would you change that? I don't see how.

My suggestion is that you and Charli come to an agreement. As long as she knows that you are not replacing her mother, the title she uses is immaterial. And apart from Charli, use your relationship with her to strengthen your position. Every child requires the foundations of both biological parents in their development, and as a step-parent, you provide the foundation of the missing parent. And by all means, encourage a relationship between Charli and her biological mom. And definitely find out why, all of a sudden, dad is so upset over all of this, especially since he was okay with it for the past five years.

I had a similar situation. My daughter, Stacey, was only 8 when I separated from my ex. When I hooked up with Graham, my son's father, my daughter was calling him dad until her biological father stated that he was her father not Graham . This broke her heart. As time went by, Stacey became very sneaky and called Graham, dad, when her father was not around. Now, 3 years on, Stacey still calls Graham dad. The down side is that her father is now living in South Australia andhas not been in contact with her in a year and a half.

i have never being in this situation,but the question that should be asked is why after 5 years does your step daughters mum want this stopped, sorry to be personal. and has their being a change in the way the contact visits being etc.

I think that it's all about the children, and if they are comfortable calling you mum then that's what it is.  Does she see her mother often? Does she call her mum "Mum"?  5 years is a long time, if you were new on the scene that would be understandable, but you have been 'mum' for 5 whole years.  Can I ask how old your step daughter is?