AITA For Changing My Last Name

I’m a female age 20, my parents separated when I was 3 and their divorce wasn’t finalized till I was 5. Growing up my mother was very loving and supportive to me and my two biological brothers. However my biological father choose to drink, neglect us, and do some other not so very good things. When I was 10 my mother remarried to my dad. He has shown me how a man should treat a woman and has been a great father to all of us kids. Around the time that I was 12 I completely cut my biological father out of my life. No longer wanting to deal with him. My brothers still have I think good relationships ship with our biological father. Around the time I was 15, my brothers started to push me to give my biological father a second chance. After saying no many times, I be grudgingly agreed to try and give him a second chance. We had awkward conversations and a few lunches. My biological father still didn’t seem interested in me like when I was younger. And was still doing things he did when I was kid. So are relationship has never gotten any better. Since I turned 18 I’ve been wanting to change my last name to my dad’s last name. In fact since I was 12 I’ve wanted my dad to adopt me. My family just didn’t have the money and my biological father would never allow it. Now that I am 20 and have a good paying full time job. I have been working towards this dream of mine to change my last name. I had been trying to keep it a secret but like any secret it got out. One of my brother’s thinks what I am doing is good while the other is thinks I am being the b-word. My biological father is also very unhappy and this I am being A-hole. But I don’t feel like I am and I think my dad has been a better father to me than my biological father ever has been. So AITA?