Wouldn't you need tons and tons of training data ? Obama, Clinton and Trump are public personalities, so it's easy to have many hours of recording of their voices.
A random relative; not so much.
A random relative; not so much.
http://www.aarp.org/money/scams-fraud/info-2016/how-to-beat-... https://de.wikipedia.org/wiki/Enkeltrick
If they really need a voice sample from a relative they could still impost, with voice or not, as insurance person, HR or police and acquire it by simple means if they have any idea about the social graph of their victim.