Android 17 is a human turned android like his sister Android 18. However, unlike his sister, he is more aggressive and violent. After killing Dr. Gero, he went on with Android 16 and Android 18 to try and kill Goku just for the sake of it being a game to him.
When he falls victim to Cell and was revived afterwards, Android 18 chose to live a generally peaceful life, even helping Goku and the Z fighters when he can.
His love for nature also motivated him to choose being a national park ranger as his career and even marrying a zoologist in the process. He went on to have 3 children, one born with his wife and two adopted ones.