I had sex with my brother’s ex-wife

The small backstory: I live in New Jersey, always have. My brother married his college girlfriend (lets call her Nicole). She always lived in California, my brother moved there for college and stayed there. I barely saw them and every time they would argue all the time, Nicole had a temper. I was never close with my brother or Nicole, we later had a huge falling out (My brother and I) so I stopped talking to both them. They later divorced. After I graduated (3 years later) and got my BA I went to California for a vacation and look for graduate schools.