Writers have two kinds of relatives: those who fear turning up in the writer's stories and those who fear not turning up there. My sister Kate, whom I adore, has always complained that I never put her in my fiction. I have tried; once I named a hurricane after her. She said that was not going to cover it. Some people are never happy.
So I tried to put her in my China story, but she won't fit. For the female character, I need a bossy pragmatist, and Kate is a sweet-natured (usually) romantic. But if I had put her in, and it was an unflattering treatment, what then? J.P. Donleavy said that if you publish your first novel and nobody sues you, you haven't been honest enough. Might be a bit of an exaggeration.
Anyway, Kate wouldn't sue me. I know too much about her (and vice-versa). Between sisters, these things are handled more discreetly. By blackmail.