Answer your question about Vietnamese family names:
Ancient Vietnamese have no written language.
When the Chinese came to Vietnam about 2 thousand years ago,
they taught their written language and Chinese characters. They
also called the Vietnamese names in Chinese, writting the Vietnamese
names in Chinese characters. Then the ancient Vietnamese learnt
Chinese, speaking Chinese with their own accent that the Chinese
cannot understand, and even pronouncing Chinese characters in
pure Vietnamese. That is the reason the Vietnamese names can be
written in Chinese characters, and can be read in either of the 3 ways:
pure Chinese accent, Chinese with Vietnamese accent, and pure
There is one thing you may need to know:
There are thousands of thousands of Chinese who have migrated
and stayed in Vietnam since then . However, there are only few
Chinese who can speak Chinese, and remember the old place in
China their parents come from. So, physically, many Vietnamese
nowadays may be Chinese, but spiritually, they are Vietnamese .
These Chinese have lost their own identity, and put on the identity
of local people who accepted them and loved them as brothers and
In the world of human being, there are always good people who
think positively about people, and bad people who think negatively.
May be they just don't want to associate with the painful past that they left behind?