I see your point, but even changing your name, you can't escape the fact that you and your "half brothers" are just brothers. In spanish, brother is "hermano" but there is no word for "half-brother", as regardless of whether you have the same mother or father, you are just brothers. There is the word "hermanastro", used when there is no common blood, like if your dad marries a woman who already have offspring with some other man.
Changing your name you are not only refusing your brothers, you are refusing your dad too. Don't take no offence for what I tell you, but changing your name is not like coming and going of a forum, you have to understand the implications -and the legal implications are the least important in my opinion-. You are yourself, your name is a social thing and you won't be somebody different from changing your name, you will be the same and your brothers will still be your brothers, and you can't change your bloodline from changing your name.
Just my 2 cents, you know.