I am estranged from my only sibling, due to our toxic, narcissistic mother.
Brother and I were best friends as teens - he knew our mother was toxic, I did not at that point. He tried to warn me, I thought it was sour grapes.
So our mother played favourites. Whichever child was doing what she wanted, obeying her etc, was the favourite. That was me. I was a terribly shy child, so I did what she wanted and she showered me with attention and affection. I was very much a people (mother) pleaser. If you disobeyed Mother, well, she cut you off.
As bro and I got older, mother started false rumours and innuendo to drive a wedge between us. Knowing, that we wouldn't ask questions, we just went along with it, believing the other was badmouthing us. By the time we were late 20's/early 30's, Bro and I barely spoke. This is exactly what mother wanted.
Middle aged now & Mother continues her divide and conquer, however sadly, my brother believes her BS and is under her spell as he is now "the golden child". I cannot reconcile how any parent would deliberately set out to sabotage and ruin their child's siblings relationship but mother has. She gloats about it.
Its too late for us; I lost my brother a long time ago. He is now someone I do not recognise. I did call mother out once, about 10 years ago. She told me my brother said something about me, so I called my bro, then and there and asked him "did you say x, y or z". He laughed and said "ofcourse not". This caused a massive fallout, as our father recognised what mother had done and was subsequently very angry with her. So, she got her just desserts. Once.