I NEED ADVICE

So I was dating this one guy who was older than me and he has a brother that is in my grade. I’ve always thought his brother was cute and we’re really good friends but then his older brother broke up with me and he’s always been there for me and I’ve realized that I really like him and dating his brother was a mistake. However, I feel like a horrible person and I feel like his parents would hate me if we ever dated because I dated their other son please help!!!