I'd agree with Hilbunnyb.

If moving out is impossible and the gang won't let go it might be possible to buy him out, however that is an extremely risky strategy and might only serve to pinpoint a source of cash. If that sort of cash is available it might be better to knock the person out, stick them on a plane far away and keep their passport so he can't get back.

Best of luck for your friend and their relative.