I'm sorry you feel this way. I too have had similar thoughts in the past but not so much now that I'm trying to find my own meaning and purpose for being alive. If we only had value because of the people we happened to be born to, how very sad it would be.

You are a beautiful human being of equal value to any of us. You were created the same way as everyone else and are made of the same stardust as we are. Sadly, like a lot of people, you were born to people with serious issues who didn't value you probably because they didn't value themselves or life either.

While it's hard, there is another way. You can look around you now and make your own purpose for being here. You are so worthy and it's just up to you to embrace that worthiness no matter what your origins happened to be. I appreciate it's not easy and experiences like yours definitely can't be shrugged off, but it can get easier once you realise nothing you went through was your fault or a reflection of who you are.