However more recent research has led to the claim that he was born a Tibetan in Kharta valley , Tibet , but his family were left destitute when their yaks were killed by disease , and he was sold as a bonded servant to a Sherpa family in Thamey in Nepal . However more recent research has led to the claim that he was born a Tibetan in Kharta valley , Tibet , but his family were left destitute when their yaks were killed by disease , and he was sold as a bonded servant to a Sherpa family in Thamel in Nepal .