In some fan circles, Giovanni's ruthless and cuthroat behavior has thought to have stemmed from a cruel childhood. This past is never mentioned in the game and from what I have read of the many manga series, not much is discussed there either. The only hints we have of his mysterious past are in the drama CDs based on the anime prequel to the first movie. The enigmatic figure that haunts Giovanni's past is none other than his own mother, simply called Madame Boss (Or Lady Boss).
We know that Madame Boss was as much, if not more, a ruthless Rocket Leader as Giovanni. This gives insight to perhaps how Giovanni came to be. Madame Boss was not quite as involved in gathering rare Pokemon as much as she wanted to make money with Team Rocket. Her plans are unknown but could be gathered that there was not much to them. (Let us say Giovanni did not inherit his tactile way of thinking from his mother.) Unlike Madame Boss, Giovanni was able to control Team Rocket in a way she never could and had several schemes to come into fruition before his fall.
When one looks into his past with this character, he almost becomes a tragic character. One could speculate how he grew up, in a criminal family where he never was able to learn right from wrong, perhaps he is the way he is because of the lack of taught morals? We also know that Madame Boss was not entirely fond of her son. And why was that? Was he inept in some way? We he a child of illegitimacy? Did he spawn thoughts of her past that she wished to forget? Whatever the case, we know that Madame boss constantly ridiculed Giovanni and put him down, even into his adult years.
And what happened to Madame Boss? She was mentioned so briefly. Perhaps it is to have the audience have some sort of emotional relationship with Giovanni. Was his past so painful that it had to be hidden? To not be recalled? Did something tragic happen to Madame Boss or was a crime, so horrible, committed that it was never to be spoken of?