My soon to be step-son has called me by my first name for the last 2 years, but that has changed recently..We are going to be married next summer and I explained to him that I was going to be his step dad. Now he says Mom and dad sometimes and 'your gonna be my step dad' so we are not sure what he will call me, but we are fine with whatever he chooses. I am sure the ex will not like it, but get over it.