Does parent abandonment effect more in childhood or adulthood?

I think childhood because my mom abandoned us when I was a child (age 5), and she wanted to have her own life and only thinks of herself. I haven't seen her since I was 20. I'll be 30 next year so it will be 10 years. She lives on the same state. My brother wants NOTHING to do with her and refuses to be nice to her. When I bring up mom, he gets hostile changes the subject. He doesn't care.
Anyways when I see people with their loving, amazing mothers, I feel like shunning them and hatred. My mom had so many chances to be in our lives but she NEVER takes them! She never returns my calls when I call her or wishes us a happy birthday.