I wanna go on record as the first person to make this connection. I believe that Rockstar recognised it was impossible to craft a Nico Bellic who was trying to turn his life around, while also being a crime-lord and wrecking shit in helicopters. I think splitting him into 3 seperate entities is their solution for this, as he literally represents the three re-occurring dissonant roles of the Grand Theft Auto protagonists (and empathic in-roads for different player motives) so far.
Below I have provided a character bio of Michael, Franklin and Trevor for referrence, taken from the unofficial wiki:
As the smartest one and the self-proclaimed leader of the Powerpuff Girls, she is often seen as the most mature, level-headed and composed member of the group, although she can also be fussy, overbearing, vain, and overly analytical at times. She tends to "mother" Bubbles and Buttercup, and often tries to play peacemaker between the two if they fight but ironically she is quick to argue with Buttercup who acts on impulse as opposed to her analytical nature. She is naturally caring to mainly her sisters, but also the Professor as well. In "A Very Special Blossom," we are shown a darker side to Blossom when she resorts to stealing the Pro-Excellence 2000 Golf Clubs for the Professor, who later says it's his fault for putting too much value in a material item instead of the love for the Girls. For this, her first (and fortunately only) offense, Blossom was sentenced to 200 hours of community service, which was a harsh reminder to her and to all that crime doesn't pay.
The ending theme refers to her as "the joy and laughter," meaning that she is defined by a sweet, cheery, mild crybaby and gentle demeanor. She takes the role as the youngest out of the girls. Bubbles does, however, have a tendency to be overemotional, despite the fact of her having a habit to be ditzy, naive and sensitive leading to her sometimes being regarded as the group's weakest link, by friends and foes alike. However, she can become very independent and aggressive, let alone extremely mad when pushed. Out of all the Powerpuff Girls she is the most feared by Mojo Jojo after having single-handedly taken him down in a fit of rage in the episode Bubblevicious. Her special superpowers are the Sonic Scream, understanding various foreign languages, and communicating with animals.
Referred to in the ending theme as "the toughest fighter," she is the group's tough one and is easily enraged. Sometimes this, and her aggression gets the better of her, making her a little reckless and stubborn (but she overcame it in "Makes Zen To Me"). She also showed a greedy side in "Moral Decay," to which she knocked out all of bad guys' teeth for money earns. She has shown these sides, and a softer side in several episodes. For example, in the episode "Cover Up," she had a soft green blanket that she was obsessed with that she would hug that gave her the confidence to be a better fighter, and she is quite protective over her sisters. She possesses a violent and mean streak not displayed by her sisters.
With this in mind, my favourite character is Franklin: the toughest fighter!