I'm thinking of quitting a job my friend got for me
What doesn't you like about the job?
It pays too little and I don't really like it. The boss isn't cool.
Well, it sounds like you're right in leaving it then.  Nothing says you need to stay at a job you don't like.  Just make sure to give them notice!
I don't want to do that and I'm just going to abscond.
If you do that, it will affect your brother's reputation and those people will not trust him anymore. It'll also be inconvenient for your company if you quit it without a notice. You should think about what i just said.