Who was Monks? What did he ask Fagin to do with Oliver and why?

Monks is a minor character and villain in the story. He is actually the half-brother of Oliver Twist, but he hides his identity. The father's will favors Oliver, and not Monks. There is a catch though: if Oliver should ever commit a crime, he will be automatically disinherited, and everything in the will goes to Monks. Monks wants Fagin to keep Oliver's identity a secret so he (Monks) can claim all the inheritance.