Wow. Your father and cousin seem like jerks tbh. I kinda understand why you seem to have difficulty accepting your stutter when the people around you aren't helping at all. I'm sorry that I can't offer any specific advice, but maybe try to find a new circle of friends that will accept you for who you are. Having people who accept you does wonders for your self esteem. Hang in there buddy, we've all been there at some point in our lives.