That's what I was thinking in terms of alterior motives before the kids. "See kids, see how nice I am, I buy her gifts for mother's day, she doesn't bother to buy one for me, even if it is from you guys". Kinda messed up in my opinion.
However, I see refusing the gifts equally as bad. Think about it. "Kids, I just don't understand your step-mother, here I go and do something nice like buy her a gift and she sticks her nose up in the air about it and won't accept it."
I think the best solution is talk to the ex-wife. If she insists on buying the step-mom a gift, then she has to be willing to accept one in return. Otherwise, if she doesn't want a gift from the new wife, thats all fine and dandy, then she needs to cease buying gifts herself.
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