Screaming kid, and parenting

So here's the deal. My 2 year old brother screams when he doesn't get his way. Sometimes it's because of a sippy, and sometimes it's because he gets told no for something. Sometimes he gets spankings from his parents (barely ever) or he is put in his room. Sometimes we give him a sippy if he asks without freaking out and screaming buuuut my other siblings get annoyed and give it to him anyway. My boyfriend (when my baby brother got put in the bedroom) says "our kid will not be acting like that because I'll whoop that ass." I then told him 'you don't know how he's going to act reguardless of the discipline that's given to him because every child is different.' I have some questions...how do you feel about it? What would you do? What's the best way to handle a screaming toddler?