What do you do about a step parent that acts like your actual parent?

My step mother was very kind and patient with my brother and me. And her/ their own 3 sons. She sort of approached us as a friend but she was a mother first. My dad left town when I was 5 and came back when i was going on 13 remarried with 2 boys and then had another. We called her by her first name, but politely. I never resented her. The old man had a way with words. Hee may have used half brothers once then somehow the half thing or step thing was unnecessary waste of air. My youngest brother is seventeen years younger than I am. In a way I don't know him real sell he as always busy with his age group. But we're brothers.