I think everyone's entitled to their opinion here. As for me, though: my brother died at 10 years old (back in the 90s). While there are some home videos with him talking, it's never for more than a few seconds at a time.

Maybe a decade ago, I came across a cassette tape that he had used to record himself reading from a book for school - several minutes in duration.

It was incredibly surprising to me how much he sounded like my older brother. It was a very emotional experience, but personally, I can't imagine using that recording to bootstrap a model whereby I could produce more of his "voice".