My child talks about their “brothers and sisters” often. They don’t have brothers and sisters. They have step brothers and half sisters. I’m sick of constantly having to correct them and then explain to other people the family dynamic because they are obviously confused. Several people agree with me as shown in my poll. They just haven’t spoken up yet.
I absolutely do not agree with you. When I was pregnant with my eldest DD, my then SDD would say happily that she was having a baby brother or sister. Then she started saying that the baby would "only" be her half brother or sister. I gently said that yes, they only shared a dad but one day the baby would have other siblings and if SDD wanted to choose to be the odd one out, that was up to her,but in my mind,none of them were "half a person". It was her Mum trying to diminish the relationship they would have and more harmful to SDD than anyone,I guess.
As it is, I did not have more DC with him, he left me and I had 2 more DC with my partner of 20 years.
My eldest DD doesn't have a relationship at all with her older sister but is very close to her younger siblings. My DP is very much an involved Grandparent to my eldest DDs children, has my eldest DDs name tattooed on his arm and I have been told by DD that if ever we split (not on the cards) she will not choose between us.
I think you will only cause upset by constantly correcting your DC on this. It is not about what you want or what is "factual", you are coming across as bitter and that is never positive.
As for being a MW and someone saying in front of you to their DC, obviously that was done to explain to you.
"It's hard when you're hurt" I get that.... think of it as a kindness you are doing for your DC and in the long term, for yourself. They will pick up on the bitterness and that will not be good for your relationship with them.