AITAH for not wanting to take my dead brothers kids?

This situation is so shitty and I really need advice.

Me 31(M) live on my own in the city. My brother 34(M) and I have always had a strained relationship. A little background is that my brother is basically a diagnosed narcissist and growing up with him was extremely difficult. He had it out for me since I was born and would bully me at any chance he gets. We went to a K-12  private school and he would try and make my life a living hell for the entire time I went there. For  example  when I was playing soccer he would show up to my games and literally pants me in front of everyone. He would fart on my pillow, spread  terrible rumors about me,  and make sure that absolutely no one wanted to associate with me. It got so bad that in my sophomore year my parents had to switch me from the school that my family had been attending for generations to a different school two towns away. Once he went to college I went absolutely no contact with him except for mandatory holidays  and family gatherings which up until now he would still go out of his way to humiliate me any chance he got. He  would say that I was a worthless man for not having children and that I would contribute nothing to society and that my entire existence is unnecessary.

Flash forward to present day My brother was married with two daughters who are 6 and 3. Last week him and his wife got into a fatal car accident that tragically took both of their lives. Obviously this is a devastating situation and I feel terrible that it happened but my brother and I had a terrible relationship and based on how often I saw him he was more like a stranger than family. The funeral is set to happen this weekend and me and my girlfriend will attend. The problem is that my mom just called me telling me the most shocking and confusing news I have ever received. My brother and his wife had named me their kids godfather and wanted me to be their legal guardian if anything were to ever happen to them. I was never made aware of this or  agreed at all and I do not  want the kids. Me and my girlfriend just moved into an apartment together and have discussed our mutual agreement for not wanting kids. We are  just settling  into moving in with each other and are not comfortable taking the kids. I want to make this clear to my parents but they are very upset and I’m not sure  how I should go about this. I am  facing a lot of pressure from my other relatives to take the kids but it's non negotiable for me. How do I tell them and AITAH for not wanting to take my dead brothers kids?