The mother, who shares a son with her husband, took to the site with her dilemma, saying: "I've got two great stepkids, dear son, 11, and dear daughter, eight, and me and dear husband have a son, three, together. We've been married for six years."
She explained: "Parents get on fine, not very friendly but no dramas with dear husband's ex-wife who remarried two years ago.
"Last weekend dear son, 11, came to me and sheepishly asked if I'd be OK with him calling me Mum as well as his 'real' mum."
She went on: "I didn't think twice and said yes, but ex-wife has text husband and said that she's told the kids to call me by my name as I'm not their mum and that she expects husband and I to tell them the same...".
Seeking advice, she wrote: "Am I being unreasonable to just ignore her or should we have a chat with daughter and son? Really don't want to cause any grief which would impact on the kids, certainly don't want them in the middle of a parental spat?"
Other users criticised her online for the post, with some suggesting it was 'nasty and cruel' not to understand where her partner's ex was coming from.
One wrote: "How awful to even think about taking the name of a mum like that. It's not appropriate. I find it actually cruel and nasty to even consider it."
They added: "You're not their mother, you haven't adopted them. They have a mum. Don't be so mean."
Another commented: "You are not their mum though, she is. She will always be their Mum. You will be their stepmum for as long as your marriage to their dad continues. No way should you be called Mum."
One wrote: "I wouldn't be happy with this either to be honest. Your name or some other affectionate title is more appropriate."
"How would you feel about your dear son calling someone else mum?' another user queried, adding: 'It's a big fat no from me."
And one wrote: "You're not their mum, it's a no from me."
