I've used real people in my life and they used to stay true to the people themselves, but it interfered with the story. Their personalities were too similar. So, I kept some aspects of who they are, but I've changed them for the sole purpose to make my story work better. I gave them a base personality, where they grow into themselves, instead of being a fully developed character. I gave them faults whether they were true or not. I've exaggerated parts of of their personalities as well, so that the group dynamic would change and be challenged as well depending the situation.