Michael is the main character of the story. It starts off as him and Trevor with some other friends robbing a bank. When they were going to get a chopper to escape the cops, Their friend got shot by a sniper. Michael knowing that they're was no other way out, stood in the open unpurpose so the man with the sniper can shot him too. Trevor was shocked. He didnt want to leave his bestfriend to die but Michael said he thought he was bleeding out. But little did Trevor know that Michael was actually wearing a bullet-proof vest underneath his clothes which saved his life. So Trevor ends up running away on foot thinking his best friend was dead. A cut scene shows how Michael was actually at his own "funeral" looking at the people who were attending. Michael later on changed his name from Micheal Townsley to Michael De Santa and remarried his wife Amanda to raise their 2 kids together, Jimmy and Tracey De Santa.
As you know Trevor was with Michael at the begining of the story. He and Michael were bestfriends until Michael had "Died." Michael faked his death and left Trevor on his own. Trevor moves to Sandy Shores in San Andreas, Miles away from The City to not be caught by the police. Years later he sees on the news that a secerty guard says that one of the guys who robbed a jewlery store said a quote to him, "You see a million things everyday. How about you make sure this is one of them." Trevor was triggered because his "dead" Best friend said that while robbing the bank years back when he died. Later Trevor finds a man by the name of Michael De Santa Married to a woman names Amanda (aka Micheal Townsley's ex-Wife). He gets mad because he thinks its just a random guy trying to be Michael Townsley. So he goes looking for the guy and finds out that it is actually his best friend that he thought died, now living in the city of Los Santos.
The first couple missions of story mode you have to play as Franklin. It shows how he had to rob cars with his friend Lamar for his job but later gets into some trouble running into Michael because he stole his sons car. It shows how Franklin's life is up until he becomes good friends with Michael. He then started to do some illegal work with Michael and made money off of it. His life went from living with his aunt to living in a big house up in VineWood Hills. He then on is good friend with Michael and Trevor through out the story and helps them thoughout the story.