would you let an estranged parent back into your life?

I have been on my own since I was 15. My parents were never married and split when I was three or four. They both were alcoholics and drug abusers. They live in my hometown, where all my family is from. I have seen my mom maybe a total of five times in the past 12 years. My dad maybe 3. My mom has made her choice with drugs and alcohol. She doesn't have a desire to be in my life or my children's. I've tried. Idk if it's because I'm closer to her family or a daughter wants that relationship with her mom. Well my dad has reached out to me several times and I just had no desire to build a relationship with him... I feel like I have more emotions towards the cashier at target. He keeps trying though so I'm starting to think maybe I should let him in... has anyone dealt with anything like this? I'm just kind of looking for some advice from an outside source or words of encouragement. Thank you