I got with my husband while he was going through a divorce. He had a son who had just turned 2 when I moved in with them. One night after we finished reading to his son and putting him to sleep my SO asked me if I would like his son to call me "mom". At the time I didn't know too much about his ex-wife and didn't really know how long or if our relationship was going to last also I had grown up with multiple stepfathers in my life and didn't like calling them "dad" so I said "No, he already has a mother he can just call me by my name".