I was difficult for my parents to raise and I know they've had issues with me. We even went to family therapy for it when I was a teen. They still have trouble with me since I seem to have needed rescuing from various situations throughout my life, and they've stepped in to help. I accept that perhaps I've been more difficult than my sister for various reasons. I know it's not my fault that I've struggled with mental health issues and have had some problems that have resulted.

It's not your fault that you've had to contend with some issues in life (assuming you have) or with any mental health issues. If it's been difficult for your parents, it's just because it can be. But that doesn't mean they don't love you. Give yourself a big hug and a healthy dose of self compassion.