I'm going to refuse to associate with my cousin because he won't denounce his gang or get a legal job
Specifically what about your cousin makes you not want to associate with him?
I hate him for living a destructive lifestyle...
I can understand how you are feeling. You shouldn't stand by family members that are toxic to you. You don't want their problems to come back on you and get you into trouble as well.
I think that he needs guidance. I'll still hang with him but I will try to find another way to make him go straight
Your loyalty is pretty obvious but make sure you're not putting yourself in harm by standing by them. I'm sure they'll be receptive to you supporting them and might be more open to changing their ways in response.