I’m going to get married in a couple of months to my beautiful fiancé. My dad and I just bought black suits for the occasion (my groomsmen and I are going to do a “blackout” for the wedding). I just found out that my fiancé’s father is going to be wearing a tuxedo. When I told my parents, they were very angry and told me that either he would have to wear something different or my father and I would have to wear tuxedos as well. When I told my fiancé what happened, she told her parents and now everyone is angry. It may be important to note that my fiancé and her family are from Mexico. My question is, would it look bad if my father and I were in suits while the father of the bride is dressed in a tux? Is there some sort of unwritten rule? Thank you so much to everyone, I really need help.

There is no rule. Except that normally the bride will decide most wedding choices, including "dress codes or rules"

But most do not unless they are going to require specific types or colors.

It is silly to get upset about someone wanting to wear a tux. (which from history is the normal suit for men at a formal wedding)