Michael De Santa is the currently unnamed protagonist of Grand Theft Auto V.
Biography
Background
Judging by what he says in the trailer he was once a criminal. He left that line of work and moved to Los Santos, presumably he was wealthy as he mentioned buying a big house, to live a normal life with his family. He mentions having children whom he wants to be like the children on TV.
For a currently unknown reason he decided to return to a life of crime, at some point robbing a bank with two unknown accomplices.