Dear Spooked -
Death in dreams tends to symbolize “change” and “going away.” Accordingly, I do not believe you want to “kill” your brother. Rather, I think a part of you does wish that the situation he has caused would “just go away.”
Perhaps you wish there was some “trick” that would allow you to break away from your relationship with your brother. Your brother’s situation has taken you by surprise - he has “spooked” you. Lo and behold you push this relative away from you, and the “trick table” works perfectly. Your brother is broken away from you - for good!
Dreams allow us to “see” feelings and awarenesses that we hold within us that we might not realize, or want to admit. Given the context of your dream, I think it is clear that you have some anger and resentment toward your brother due to the sudden, and unsolicited, burden he is putting on your family. I would caution you from translating your brother's death too literally.
Try talking openly about your feelings with your wife. Together, you both need to make decisions about how far you both are willing to let your brother’s affairs intrude into your own lives. And be sure to factor your children’s feelings into your decision-making! Best of luck.