I've been with my husband 3 years (but only married recently). He has two kids aged 6 and 4. My husband's previous marriage had broken down before the youngest was born, and the kids mum decided she couldn't cope and left a few months after that. We were very careful to introduce our relationship slowly to the kids, but we've never had any issues. They both call me mum, which I love but neither me nor my husband ever told them too. Today when I picked them up from school one of the other parents told me as a stepmum I'm wildly over stepping and damaging the kids health by calling myself their mum, especially if there biological mum comes back. Considering their mum has chosen not to be in their lives, am I right to have filled that role? Or am I actually causing them harm?