I know this is a website for brides but I wanted to know as a future best man in my brothers wedding, how do I handle the emotion of knowing my brother is happy, but I literally hate his future life partners guts
Do you know why you hate her? Is it because of the way she treats your brother? Is her personality very different from yours? Is she financially irresponsible, or something else? Once you identify the reason/reasons for your feelings, you need to decide if they are legitimate ones that might create future issues for your brother. If so, then you might approach your brother and express your concerns and perhaps suggest pre-marital counseling. Having a neutral third party point out issues is often better than having a family member do so. However, depending on your brother's personality, he may dismiss your concerns. Depending on the issues, some can be corrected simply by maturity, others by pre-marital or post-marital counseling. Tread lightly knowing that if you aren't careful, your brother could take the bride's side and turn against you.