I am 63 years old. In June (2012) my older daughter (age 25) wrote me in an email that she had been "a horrible sister and a terrible person toward (her younger sister)." She said she verbally and physically abused her sister (17 months younger) for years, including shoving, shaking her, grabbing her clothes, and hitting her. I asked if the younger one had ever "fought back" and she said no, she would just turn away. She told me that when she was a senior in HS she wrote a letter to her sister apologizing and saying she didn't deserve what she did to her. I grew up a lonely only child and always wanted to have more than one child, now I am so sorry I should have stopped after my first child, my son. I knew my two girls never got along, and I tried to tell myself it was "sibling rivalry" - but now I know it was so much worse. When I told my younger daughter about this, and asked her why she didn't come to me (or to her dad) - she said, "I thought you knew". This has broken my heart. I can't stop thinking about it, and I don't forgive myself for having ignored this for so many years. Ironically, the older sister ended up having a breakdown and was diagnosed with bipolar disorder, and she is very kind to me but she has a sad lonely live. The younger sister is a high achiever with a great job - but she is very cold to me - very distant, and I fear she will never forgive either me or her sister. I am so, so sad. I don't know how to manage - I used to think I had been a "good enough" parent, and I have a good relationship with my oldest son, but now I know I failed both my daughters. The older one told me, she felt very ashamed after she would abuse her sister, so she was hurting, too. And I DIDNT EVEN NOTICE. I hate myself for that.