Believe me when I tell you this, they never change. It's not about who is the parent or not, it's a control issue to them. My hubby's ex can't stand the thought of me being a parental figure to either of my stepkids.
Case in point: My stepson is in Baghdad right now. Went in March, was part of the ground war, leaves approximately late Jan, 2004. In the entire time he has been there, I have written him app 20 letters and sent him several boxes of things. One box included 3 dozen cookies that he asked me to bake for him.
His mother, his actual birth mom, the one who tried to take hubby's visitation from him because she felt I was a danger to them (she married a convicted felon, but that never mattered), the one who has repeated to anyone who would listen that she is the good mother, I am just the slut their father married, has sent him one postcard. ONE POSTCARD! And that post card was to tell him she was sending him a box of stuff (he's still waiting for it, tho the card was sent in June) and to demand that he no longer call me or his father, that he is to call JUST HER. Should he refuse to comply with her directive, he is no longer a part of her family. He will be 22 in January and she is still trying to do this sh--, er, stuff.
My stepson has referred to me in letters to me, his dad, his sister, his fiancee AND his mother, that I am one of his parents.
He basically rolls his eyes when she pulls her crap and we have a deal that when his mom can hear it, read it, etc., he doesn't refer to me as anything other than Nancy. It keeps his life peaceful.
But he knows where the real caring and love come from. He knows who wants him around because he's a member of the family, not because he's a source of revenue.