I have two step daughters. Their father and I have full custody but they still see their biological mother every other weekend. The youngest was 1.5yo and the oldest was 5 when we met, they are now 5 and 9. The youngest has been calling me mom since she started talking, mostly because she was copying my son (who also lives with us full time).

The girls' biological mother has recently been throwing a fit that the youngest calls me mom (though she's been doing it for three years so idk why she's only saying something about it now). My husband and I never told her to call me mom, she just does it. The oldest step daughter calls me by my name, which is fine, I'm not going to make anyone call me mom.

I've explained to their mother that I never told her call me mom and she's been doing it for so long now that I'm not going to tell her she can't call me mom. I don't think we should tell her to stop calling me mom since it was something she started on her own and has been doing for three years. Any thoughts?