Vietnamese name usually is a combination of three elements: family name, middle name and given name. The most famous name example is: Ho Chi Minh. All are written separately, as above.
Quantity of family names in Vietnamese language is impressively … modest in number. An individual can count by memory something more or less 20 typical Vietnamese family names.
Most common surnames in Vietnam are Nguyen, Tran, Ho, Pham, etc. One polular joke stated that up to 50% of Vietnamese are Nguyens, 40% are Trans, the rest 10% are represented by all other family names.
Although it is not very accurate counting data, but more or less you feel it can be true, when you are reading namelist of Vietnamese participants.
All this bearer’s of one family name are not relatives at all.
Vietnam: male names
Vietnam: female names
Vietnam: unisex names
Vietnam: children names
Vietnam: business names
Vietnam: star names