I will start with James. James was a good, happy, rich boy who got everything that he wanted, that is, he almost got everything that he wanted. He got anything and everything that was sold at stores and markets, but what he never had was love. Whenever he felt lonely, he had his pet Growlithe, Growly and his lucky bottle caps that always made him feel better, but bottle caps and the affection of a Pokemon wasn't enough. Both of his parents controlled his every action, including the person that he had to marry. This was too much for him, and so he ran away from home taking only some money and his lucky bottle caps.
Jessie, however, was on the opposite end of the social ladder. She was poor and only had her kind mother, a few precious toys, and her hair. These were her only friends. Eventually she lost each of these. Her mother to a murderer (most likely her father that abandoned them), he favorite toy to a Jynx (which was just trying to fix it), and her hair to a Scyther. This nice, poor, little girl had everything taken from her. So she had to take things back.
Now these two seemingly parallel lives meet. And for the rest of their lives, through all hardships, they stayed together. They met at the place called Pokemon Tech. James saw Jessie, and it was love at first sight. Jessie told her story to James and James told her that he would pay her and his way through Pokemon Tech (with some of his parents money). However, they both flunked out. It didn't matter to them, they wanted to look for something more exciting.
So they traveled to Sunny Town and joined the local Bicycle Gang. Jessie was happy for a little while as Big Jess, and James was also happy being Trainer Jim. However, this quickly got boring. They wanted to take revenge on the world for the love that it had never shown them. They tried to find some love in Team Rocket, but they never did. All they got was more sorrow and anger. Enter Meowth.
Meowth brought happiness to Jessie and James, for a while. Meowth, too never truly knew what love was. Ever since he was a kitten, Meowth was abused. It had a dream of going to Hollywood, and so it did. Yet, the only thing that it got Hollywood was even more sorrow. He as well met up with a gang. Then...he met Meowsie. He was in love with Meowsie at first site as well. But this wasn't the same love. It was a false love that was only skin deep, only physical. However, Meowth was still determined to get Meowsie's love. He learned to walk and talk like a human. When he showed her his new talents, it only disgusted her. Meowth vowed to take revenge on the world for never showing him any kindness or compassion. So he joined Team Rocket. Jessie, James, and Meowth may not seem like the best of friends. They have little squabbles very often. Nothing very major. Except for one time when Meowth was once again tempted. This time not by love either, but by riches and power. When Jessie and James washed up on shore, Meowth knew that they would ruin everything by taking him away from all of his riches. So he told the people of the island to toss them back into the sea. Jessie and James were a little mad at Meowth, but then realized that if their friend truly was happy, that they should just let him be. However, when the people giving Meowth riches realized that Meowth wasn't the Meowth of Bounty because it couldn't use the Pay Day attack (in Pay Day, a Pokemon claws at another Pokemon and money somehow comes out) they made Meowth go to the stadium, to fight some Pokemon, and try to remember Pay Day. Meowth never learned Pay Day because it used all of it's memory up learning how to walk and talk. Meowth was being beaten and bruised by all the Pokemon that it was fighting and when Jessie and James saw this, they knew that they had to help out their friend on last time. They hid under a corridor and through all of their money (all in coin form) out into the stadium. When they realized that they hadn't thrown enough money, James through his lucky bottle caps that meant so much to him (he did so because they were in the shapes of coins). Meowth was amazed to see that all of these coins had appeared when he knew that he didn't know Pay Day. When the coins were presented in front of him, he saw one coin that looked peculiar. He inspected it and realized that it was one of the bottle caps that James treasured so dearly. He ran off to the sea and rejoined with the only two people who actually ever loved him.
Team Rocket truly isn't evil. They just stand out in a world that they believed never loved them. Trying to find love through other things. But, there is only one that Jesse, James, and Meowth truly have. And that is for each other.