Why is my youngest brother (age 8) so mean? I cant take it anymore. It's tearing my family down.?

My guess is your brother is trying to emulate and/or gain the approval of a role model in his life, and believes this behaviour will achieve that. Alternatively he's just trying to get his way and he's learned that this behaviour works. If your dad's not available to stop him, are there any others he would look up to and listen to? Can you work with your ma together, and maybe even your extended family also, to rein in his behaviour?